Amazon Coding Interview Questions: 914 Tagged Problems

914 coding problems tagged Amazon — 347 easy · 428 medium · 139 hard — with solutions in 13 languages. Plus a 4-week study plan by topic.

Problems: 914
By difficulty: 347 easy · 428 medium · 139 hard
Languages: JavaScript, TypeScript, Python, Java, C++, C, C#, Go, Kotlin, Swift, Rust, PHP and Ruby
Cost: Free on every plan; sign in to run and submit

914 problems the CodeKairo catalogue tags as commonly asked in Amazon's coding rounds — 347 easy, 428 medium and 139 hard — each judged by hidden tests in 13 languages. The most common topics among them are Arrays (552), Strings (238) and Math (185). Tagged for Amazon and no other company: Maximum Population Year, Minimum Subsequence in Non-Increasing Order and Find Lucky Integer in an Array. At 83% of the catalogue the tag is a broad net rather than a shortlist; the pattern below is the narrower place to start. CodeKairo's Amazon — SDE Online Assessment mock covers the Amazon SDE online assessment pattern: code debugging, then two coding problems, then logical reasoning, which are the three parts of the assessment that can be reproduced. The tag is the catalogue's own annotation of where a problem tends to come up — not a list published by Amazon, which CodeKairo is not affiliated with.

Amazon study plan by topic

40 of the 914 problems tagged Amazon over 4 weeks, about 18 h 5 min of solving, grouped by technique in the order they build on each other — Arrays, Strings, Hash Table and Counting and 24 more. It ends with the Amazon — SDE Online Assessment mock.

Week 1: Arrays, Strings, Hash Table +4

11 problems on Arrays, Strings, Hash Table, Counting, Math, Two Pointers and Sliding Window, easiest first within each topic.

Shuffle the Array Easy
Length of Last Word Easy
Detect Capital Easy
Jewels and Stones Easy
Valid Anagram Easy
Number of Good Pairs Easy
Reverse Integer Medium
Reverse String Easy
Merge Strings Alternately Easy
Minimum Difference Between Highest and Lowest of K Scores Easy
Contains Duplicate II Easy

Week 2: Prefix Sum, Sorting, Counting Sort +5

11 problems on Prefix Sum, Sorting, Counting Sort, Binary Search, Stack, Queue, Monotonic Stack and Matrix, easiest first within each topic.

Running Sum of 1d Array Easy
Find Pivot Index Easy
Largest Perimeter Triangle Easy
Third Maximum Number Easy
How Many Numbers Are Smaller Than the Current Number Easy
Count Pairs Whose Sum is Less than Target Easy
Minimum Common Value Easy
Baseball Game Easy
First Unique Character in a String Easy
Number of Visible People in a Queue Hard
Unique Paths II Medium

Week 3: Simulation, Enumeration, Greedy +6

12 problems on Simulation, Enumeration, Greedy, Heap, Bit Manipulation, Number Theory, Combinatorics, Graph and Breadth-First Search, easiest first within each topic.

Week 4: Union Find, Dynamic Programming, Game Theory +1

6 problems on Union Find, Dynamic Programming, Game Theory and Brainteaser, easiest first within each topic.

Surrounded Regions Medium
Best Time to Buy and Sell Stock III Hard
Distinct Subsequences Hard
Palindrome Partitioning II Hard
Stone Game III Hard
Divisor Game Easy

Finally: the timed test

Sit the Amazon — SDE Online Assessment mock under the clock — the coding problems are only one part of the round.

Take the Amazon — SDE Online Assessment mock

Amazon test patterns

Amazon — SDE Online Assessment pattern guide and timed mock

All problems tagged Amazon

Easy (347)

Find the Original Typed String I String
Special Array I Array
Type of Triangle Array, Math, Sorting
Find the Losers of the Circular Game Array, Hash Table, Simulation
Form Smallest Number From Two Digit Arrays Array, Hash Table, Enumeration
Delete Greatest Value in Each Row Array, Matrix, Sorting
The Employee That Worked on the Longest Task Array
Calculate Delayed Arrival Time Math
Most Frequent Even Element Array, Hash Table, Counting
Rearrange Characters to Make Target String Hash Table, String, Counting
Number of Strings That Appear as Substrings in Word Array, String
Circular Sentence String
Number of Senior Citizens Array, String
Find Words Containing Character Array, String
Strong Password Checker II String
Decode the Message Hash Table, String
Count Prefixes of a Given String Array, String
Count Asterisks String
Existence of a Substring in a String and Its Reverse String, Hash Table
Number of Changing Keys String
Find the Encrypted String String, Simulation
Count the Number of Incremovable Subarrays I Array, Two Pointers, Enumeration
Modify the Matrix Array, Matrix
Find the Power of K-Size Subarrays I Array, Sliding Window
Number of Bit Changes to Make Two Integers Equal Bit Manipulation
Find the XOR of Numbers Which Appear Twice Array, Hash Table, Bit Manipulation
Apple Redistribution into Boxes Array, Greedy, Sorting
Number of Beautiful Pairs Array, Hash Table, Math
Check if Array is Good Array, Hash Table, Sorting
Neither Minimum nor Maximum Array, Sorting
Alternating Groups I Array, Sliding Window
Distribute Elements Into Two Arrays I Array, Simulation
Minimum Sum of Mountain Triplets I Array, Prefix Sum
Find the Integer Added to Array I Array, Math
Minimum Operations to Exceed Threshold Value I Array
Kids With the Greatest Number of Candies Array
Separate the Digits in an Array Array, Simulation
Find the Child Who Has the Ball After K Seconds Math, Simulation
Minimum Time Visiting All Points Array, Math, Geometry
Split the Array Array, Hash Table, Counting
Find Champion II Graph
Find Champion I Array, Matrix, Graph
Prime In Diagonal Array, Math, Matrix
Matrix Similarity After Cyclic Shifts Array, Matrix, Simulation
Maximum Difference by Remapping a Digit Math, Greedy
Determine the Winner of a Bowling Game Array, Simulation
Alternating Digit Sum Math
Best Poker Hand Array, Hash Table, Counting
Minimum Moves to Convert String String, Greedy
Maximum Height of a Triangle Array, Greedy, Enumeration
Minimum Amount of Time to Fill Cups Array, Greedy, Math
Take Gifts From the Richest Pile Array, Heap, Simulation
Sqrt(x) Math, Binary Search
Kth Missing Positive Number Array, Binary Search
Find Smallest Letter Greater Than Target Array, Binary Search
Count Subarrays of Length Three With a Condition Array, Sliding Window
Minimum Recolors to Get K Consecutive Black Blocks String, Sliding Window
Defuse the Bomb Array, Sliding Window, Simulation
Substrings of Size Three with Distinct Characters String, Hash Table, Sliding Window
Find the K-Beauty of a Number Math, String, Sliding Window
Maximum Sum Subarray of Size K Array, Sliding Window
Shortest Word Distance Array, String, Two Pointers
Find Indices With Index and Value Difference I Array, Two Pointers
Pair With Given Difference Array, Two Pointers, Sorting
Shortest Distance to Target String in a Circular Array Array, String, Two Pointers
Intersection of Multiple Arrays Array, Hash Table, Counting
DI String Match Array, Two Pointers, Greedy
Two Sum Less Than K Array, Two Pointers, Sorting
Find the Distance Value Between Two Arrays Array, Two Pointers, Binary Search
Merge Two 2D Arrays by Summing Values Array, Two Pointers
Binary Watch Bit Manipulation, Backtracking, Enumeration
Smallest Number With All Set Bits Bit Manipulation, Math
Shortest Subarray With OR at Least K I Bit Manipulation, Array, Sliding Window
Maximum Strong Pair XOR I Bit Manipulation, Array, Trie
Find the K-or of an Array Bit Manipulation, Array
Count Total Number of Colored Cells Math, Simulation
Construct the Rectangle Math, Number Theory
Count Distinct Numbers on Board Math, Simulation, Number Theory
Split With Minimum Sum Math, Greedy, Sorting
Number of Distinct Averages Array, Hash Table, Two Pointers
Counting Elements Hash Table, Array, Counting
Largest Unique Number Hash Table, Array, Sorting
Rings and Rods Hash Table, String, Bit Manipulation
Find Words That Can Be Formed by Characters Hash Table, String, Counting
Minimum Changes to Make Alternating Binary String String, Greedy
Most Common Word String, Hash Table
Check If String Is a Prefix of Array String, Array
Valid Word Abbreviation String, Two Pointers
Reverse String II String, Two Pointers
Largest Substring Between Two Equal Characters String, Hash Table
Count Pairs With Given Sum Array, Hash Table
Sort the People Array, Sorting, Hash Table
Common Elements in Three Sorted Arrays Array, Two Pointers
Convert Array Into Zig-Zag Fashion Array, Greedy
Wave Array Array, Sorting
Find the Distinct Difference Array Array, Hash Table, Prefix Sum
Maximum Ascending Subarray Sum Array
Find the Difference of Two Arrays Array, Hash Table
Largest Positive Integer That Exists With Its Negative Array, Hash Table, Two Pointers
Maximum Number of Pairs in Array Array, Hash Table, Counting
Rank Transform of an Array Array, Hash Table, Sorting
N-Repeated Element in Size 2N Array Array, Hash Table
Find Common Characters Array, String, Hash Table
Keyboard Row Array, String, Hash Table
Minimum Index Sum of Two Lists Array, String, Hash Table
Count Elements With Maximum Frequency Array, Hash Table, Counting
Sum of Unique Elements Array, Hash Table, Counting
Unique Number of Occurrences Array, Hash Table
Count the Digits That Divide a Number Math
Number of Common Factors Math, Number Theory, Enumeration
Smallest Even Multiple Math, Number Theory
Count Symmetric Integers Math, Enumeration
Remove Trailing Zeros From a String String
Maximum Odd Binary Number String, Greedy
Points That Intersect With Cars Array, Prefix Sum
Minimum Right Shifts to Sort the Array Array
Distribute Money to Maximum Children Math, Greedy
Count Tested Devices After Test Operations Array, Simulation, Counting
Ant on the Boundary Array, Prefix Sum, Simulation
Find the Maximum Achievable Number Math
Find the Winning Player in Coin Game Math, Game Theory
Furthest Point From Origin String, Greedy
Account Balance After Rounded Purchase Math
Divisible and Non-Divisible Sums Difference Math
Number of Employees Who Met the Target Array
Largest Odd Number in String String, Math, Greedy
Check If It Is a Straight Line Array, Math, Geometry
Maximum Number of Balls in a Box Math, Hash Table, Counting
Count Square Sum Triples Math, Enumeration
Count Integers With Even Digit Sum Math, Simulation
Sum of Digits in Base K Math
Sum of Digits of String After Convert String, Simulation
Three Divisors Math, Number Theory
Minimum Sum of Four Digit Number After Splitting Digits Math, Greedy, Sorting
Count of Matches in Tournament Math, Simulation
Add to Array-Form of Integer Array, Math
Permutation Difference between Two Strings String, Hash Table
Split Strings by Separator Array, String
Maximum Value of a String in an Array Array, String
Odd String Difference Array, String, Hash Table
First Letter to Appear Twice String, Hash Table
Percentage of Letter in String String
Largest 3-Same-Digit Number in String String
Minimum Number of Operations to Convert Time String, Greedy
Find First Palindromic String in the Array Array, String, Two Pointers
Capitalize the Title String
Check if All A's Appears Before All B's String
Count Common Words With One Occurrence Array, String, Hash Table
Score of a String String
Longest Nice Substring String, Divide and Conquer
Remove Palindromic Subsequences String, Two Pointers
Redistribute Characters to Make All Strings Equal Array, String, Counting
Maximum Number of Words You Can Type String, Hash Table
Check If Word Equals Summation of Two Words String, Math
Determine Color of a Chessboard Square Math, String
Replace All Digits with Characters String
Number of Different Integers in a String String, Hash Table
Maximum Repeating Substring String
Thousand Separator String
Check If a Word Occurs As a Prefix of Any Word in a Sentence String
Count Substrings with Only One Distinct Letter String, Math
Remove Vowels from a String String
Greatest Common Divisor of Strings String, Math
Verifying an Alien Dictionary Array, String, Hash Table
Goat Latin String
Unique Morse Code Words Array, String, Hash Table
Long Pressed Name String, Two Pointers
Reverse Only Letters String, Two Pointers
To Lower Case String
Divide Array Into Equal Pairs Array, Hash Table, Bit Manipulation
Count Equal and Divisible Pairs in an Array Array
Count Operations to Obtain Zero Math, Simulation
Maximum Difference Between Increasing Elements Array
Maximum Population Year Array, Prefix Sum, Counting
Minimum Distance to the Target Element Array
Minimum Operations to Make the Array Increasing Array, Greedy
Sign of the Product of an Array Array, Math
Number of Students Doing Homework at a Given Time Array
Check If All 1's Are at Least Length K Places Away Array
Teemo Attacking Array, Simulation
Minimum Subsequence in Non-Increasing Order Array, Greedy, Sorting
Count Largest Group Math, Hash Table
Find Lucky Integer in an Array Array, Hash Table, Counting
Minimum Value to Get Positive Step by Step Sum Array, Prefix Sum
Find N Unique Integers Sum up to Zero Array, Math
Replace Elements with Greatest Element on Right Side Array
Distribute Candies to People Array, Math, Simulation
Duplicate Zeros Array, Two Pointers
Partition Array Into Three Parts With Equal Sum Array, Greedy, Prefix Sum
X of a Kind in a Deck of Cards Array, Math, Number Theory
Fair Candy Swap Array, Hash Table
Monotonic Array Array
Leaders in an Array Array
Count Odd Numbers in an Interval Range Math
Water Bottles Math, Simulation
Sum of All Subset XOR Totals Array, Math, Backtracking
Count the Number of Consistent Strings Array, Hash Table, String
Find the Difference Hash Table, String, Bit Manipulation
Minimum Bit Flips to Convert Number Bit Manipulation
Binary Number with Alternating Bits Bit Manipulation
Decode XORed Array Array, Bit Manipulation
XOR Operation in an Array Math, Bit Manipulation, Simulation
Nim Game Math, Brainteaser, Game Theory
Base 7 Math
Convert a Number to Hexadecimal Math, Bit Manipulation
Prime Number of Set Bits in Binary Representation Math, Bit Manipulation
Binary Gap Bit Manipulation
Number Complement Bit Manipulation
Power of Four Math, Bit Manipulation, Recursion
Hamming Distance Bit Manipulation
Counting Bits Dynamic Programming, Bit Manipulation
Number of 1 Bits Divide and Conquer, Bit Manipulation
Minimum String Length After Removing Substrings String, Stack, Simulation
Number of Students Unable to Eat Lunch Array, Stack, Queue
Time Needed to Buy Tickets Array, Queue, Simulation
Final Prices With a Special Discount in a Shop Array, Stack, Monotonic Stack
Crawler Log Folder Array, String, Stack
Make The String Great String, Stack
Baseball Game Array, String, Stack
Sort Even and Odd Indices Independently Array, Sorting
Sort Integers by The Number of 1 Bits Array, Bit Manipulation, Sorting
Maximum Product of Three Numbers Array, Math, Sorting
Minimum Absolute Difference Array, Sorting
Sort Array by Increasing Frequency Array, Hash Table, Sorting
Maximum Score After Splitting a String String, Prefix Sum
Smallest Range I Array, Math
Largest Perimeter Triangle Array, Math, Greedy
Sort Array By Parity II Array, Two Pointers, Sorting
Minimum Cost to Move Chips to The Same Position Array, Math, Greedy
Maximum Units on a Truck Array, Greedy, Sorting
Assign Cookies Array, Two Pointers, Greedy
Divisor Game Math, Dynamic Programming, Brainteaser
Special Positions in a Binary Matrix Array, Matrix
Projection Area of 3D Shapes Array, Math, Geometry
Matrix Cells in Distance Order Array, Math, Matrix
Find Winner on a Tic Tac Toe Game Array, Hash Table, Matrix
Convert 1D Array Into 2D Array Array, Matrix, Simulation
Cells with Odd Values in a Matrix Array, Math, Simulation
Largest Local Values in a Matrix Array, Matrix
Row With Maximum Ones Array, Matrix
Check if Matrix Is X-Matrix Array, Matrix
Determine Whether Matrix Can Be Obtained By Rotation Array, Matrix
Pascal's Triangle II Array, Dynamic Programming
Number of Equivalent Domino Pairs Array, Hash Table, Counting
The K Weakest Rows in a Matrix Array, Binary Search, Sorting
Shift 2D Grid Array, Matrix, Simulation
Lucky Numbers in a Matrix Array, Matrix
Count Negative Numbers in a Sorted Matrix Array, Binary Search, Matrix
Image Smoother Array, Matrix
Flipping an Image Array, Two Pointers, Matrix
Reshape the Matrix Array, Matrix, Simulation
Toeplitz Matrix Array, Matrix
Maximum Count of Positive Integer and Negative Integer Array, Binary Search, Counting
Number of Arithmetic Triplets Array, Hash Table, Two Pointers
Difference Between Element Sum and Digit Sum of an Array Array, Math
Left and Right Sum Differences Array, Prefix Sum
Apply Operations to an Array Array, Two Pointers, Simulation
Minimum Common Value Array, Hash Table, Two Pointers
Count Pairs Whose Sum is Less than Target Array, Two Pointers, Binary Search
Minimum Number of Moves to Seat Everyone Array, Greedy, Sorting
Maximum Product Difference Between Two Pairs Array, Greedy, Sorting
Rearrange Spaces Between Words String
Special Array With X Elements Greater Than or Equal X Array, Binary Search, Sorting
Count Good Triplets Array, Enumeration
Three Consecutive Odds Array
Maximum Product of Two Elements in an Array Array, Sorting, Heap
Array Partition Array, Greedy, Sorting
Minimum Difference Between Highest and Lowest of K Scores Array, Sliding Window, Sorting
Check If N and Its Double Exist Array, Hash Table, Two Pointers
Can Make Arithmetic Progression From Sequence Array, Sorting
Shortest Distance to a Character Array, Two Pointers, String
Reverse Prefix of Word Two Pointers, String, Stack
Merge Strings Alternately Two Pointers, String
Remove Element Array, Two Pointers
Count Binary Substrings Two Pointers, String
Check If Two String Arrays Are Equivalent Array, String
Split a String in Balanced Strings String, Greedy, Counting
Remove Outermost Parentheses String, Stack
Determine if String Halves Are Alike String, Counting
Maximum Number of Balloons Hash Table, String, Counting
Unique Email Addresses Array, Hash Table, String
Rotate String String, String Matching
Buddy Strings Hash Table, String
License Key Formatting String
Number of Segments in a String String
Sorting the Sentence String, Sorting
Truncate Sentence Array, String
Check if the Sentence Is Pangram Hash Table, String
Maximum Nesting Depth of the Parentheses String, Stack
Shuffle String Array, String
Goal Parser Interpretation String
Jewels and Stones Hash Table, String
Defanging an IP Address String
Longest Palindrome Hash Table, String, Greedy
Repeated Substring Pattern String, String Matching
Detect Capital String
Length of Last Word String
Ransom Note Hash Table, String, Counting
First Unique Character in a String Hash Table, String, Queue
Reverse Vowels of a String Two Pointers, String
Reverse Words in a String III Two Pointers, String
Relative Sort Array Array, Hash Table, Sorting
Height Checker Array, Sorting, Counting Sort
Sort Array By Parity Array, Two Pointers, Sorting
Distribute Candies Array, Hash Table, Greedy
Longest Harmonious Subsequence Array, Hash Table, Sorting
Degree of an Array Array, Hash Table
Can Place Flowers Array, Greedy
Third Maximum Number Array, Sorting
Max Consecutive Ones Array
Sum of All Odd Length Subarrays Array, Math, Prefix Sum
Find the Highest Altitude Array, Prefix Sum
Create Target Array in the Given Order Array, Simulation
Decompress Run-Length Encoded List Array, Simulation
Concatenation of Array Array, Simulation
Build Array from Permutation Array, Simulation
Shuffle the Array Array
Number of Good Pairs Array, Hash Table, Math
How Many Numbers Are Smaller Than the Current Number Array, Hash Table, Counting Sort
Running Sum of 1d Array Array, Prefix Sum
Find Pivot Index Array, Prefix Sum
Set Mismatch Array, Hash Table, Bit Manipulation
Intersection of Two Arrays II Array, Hash Table, Two Pointers
Intersection of Two Arrays Array, Hash Table, Two Pointers
Contains Duplicate II Array, Hash Table, Sliding Window
Maximum 69 Number Math, Greedy
Find Numbers with Even Number of Digits Array, Math
Subtract the Product and Sum of Digits of an Integer Math
Number of Steps to Reduce a Number to Zero Math, Bit Manipulation
Self Dividing Numbers Math
Find Greatest Common Divisor of Array Array, Math, Number Theory
Perfect Number Math
N-th Tribonacci Number Math, Dynamic Programming, Memoization
Fibonacci Number Math, Dynamic Programming, Recursion
Add Strings Math, String, Simulation
Plus One Array, Math
Add Binary Math, String, Bit Manipulation
Roman to Integer Hash Table, Math, String
Excel Sheet Column Title Math, String
Excel Sheet Column Number Math, String
Power of Three Math, Recursion
Power of Two Math, Bit Manipulation
Add Digits Math, Simulation, Number Theory
Ugly Number Math
Happy Number Hash Table, Math, Two Pointers
Valid Anagram Hash Table, String, Sorting
Reverse String Two Pointers, String

Medium (428)

Make Three Strings Equal String
Minimum Number of Increments on Subarrays to Form a Target Array Array, Greedy, Dynamic Programming
Find the Winner of an Array Game Array, Simulation
Queries on a Permutation With Key Array, Binary Indexed Tree, Simulation
Corporate Flight Bookings Array, Prefix Sum
Find the Winner of the Circular Game Array, Math, Recursion
Longest Subsequence With Limited Sum Array, Binary Search, Greedy
Partition Array for Maximum Sum Array, Dynamic Programming
Stone Game VII Array, Math, Dynamic Programming
Minimum Number of Work Sessions to Finish the Tasks Array, Dynamic Programming, Bit Manipulation
Count Fertile Pyramids in a Land Array, Dynamic Programming, Matrix
Number of Ways to Divide a Long Corridor Math, String, Dynamic Programming
Maximum Number of Non-overlapping Palindrome Substrings String, Dynamic Programming, Greedy
Count Ways to Group Overlapping Ranges Array, Sorting, Math
Count Number of Ways to Place Houses Math, Dynamic Programming
Count Number of Texts Hash Table, Math, String
Number of Ways to Reach a Position After Exactly k Steps Math, Dynamic Programming, Combinatorics
Delete Characters to Make Fancy String String, Greedy
Count Number of Homogenous Substrings Math, String
Construct String With Repeat Limit Hash Table, String, Greedy
Minimum Number of Steps to Make Two Strings Anagram II Hash Table, String, Counting
Count Vowel Substrings of a String Hash Table, String, Sliding Window
Longest Substring of All Vowels in Order String, Sliding Window
Minimum Deletions to Make String Balanced String, Dynamic Programming, Stack
Minimum Length of String After Operations Hash Table, String, Counting
Minimum Number of Changes to Make Binary String Beautiful String, Greedy
Lexicographically Minimum String After Removing Stars String, Greedy, Heap (Priority Queue)
Count Substrings Starting and Ending with Given Character Math, String, Counting
Sort Vowels in a String String, Sorting
Find the Integer Added to Array II Array, Two Pointers, Sorting
Minimum Operations to Exceed Threshold Value II Array, Heap (Priority Queue), Simulation
Sum of Digit Differences of All Pairs Array, Hash Table, Math
Alternating Groups II Array, Sliding Window
Minimum Sum of Mountain Triplets II Array, Prefix Sum
Count Days Without Meetings Array, Sorting
Water Bottles II Math, Simulation
Determine the Minimum Sum of a k-avoiding Array Array, Math, Greedy
Find the Value of the Partition Array, Sorting
Maximum Value of an Ordered Triplet II Array, Prefix Sum
Process Tasks Using Servers Array, Simulation, Heap (Priority Queue)
Maximum Number of Eaten Apples Array, Greedy, Heap (Priority Queue)
K-th Smallest Prime Fraction Array, Binary Search, Sorting
Find K Pairs with Smallest Sums Array, Heap (Priority Queue)
Maximum Subsequence Score Array, Greedy, Sorting
Total Cost to Hire K Workers Array, Two Pointers, Simulation
Single-Threaded CPU Array, Sorting, Heap (Priority Queue)
Most Beautiful Item for Each Query Array, Binary Search, Sorting
Number of Orders in the Backlog Array, Simulation, Heap (Priority Queue)
Maximum Number of Events That Can Be Attended Array, Greedy, Sorting
The Number of the Smallest Unoccupied Chair Array, Hash Table, Heap (Priority Queue)
Maximal Score After Applying K Operations Array, Greedy, Heap (Priority Queue)
Find the Kth Largest Integer in the Array Array, String, Sorting
Maximum Score From Removing Stones Math, Greedy, Heap (Priority Queue)
Minimum Cost to Connect Sticks Array, Greedy, Heap (Priority Queue)
Find the Safest Path in a Grid Array, Matrix, Binary Search
Number of Ways to Arrive at Destination Graph, Dynamic Programming, Shortest Path
Course Schedule IV Graph, Topological Sort, Depth-First Search
Parallel Courses Graph, Topological Sort, Breadth-First Search
Detonate the Maximum Bombs Array, Math, Graph
The Maze II Array, Matrix, Graph
Open the Lock Array, String, Breadth-First Search
Loud and Rich Array, Graph, Topological Sort
Shortest Path with Alternating Colors Graph, Breadth-First Search
Number of Nodes in the Sub-Tree With the Same Label Hash Table, Tree, Graph
Minimum Fuel Cost to Report to the Capital Tree, Graph, Depth-First Search
Maximum Star Sum of a Graph Array, Graph, Greedy
Count the Number of Complete Components Graph, Union Find, Depth-First Search
Minimum Score of a Path Between Two Cities Graph, Union Find, Depth-First Search
Reachable Nodes With Restrictions Array, Tree, Graph
Largest Plus Sign Array, Matrix, Dynamic Programming
Remove All Ones With Row and Column Flips Array, Matrix, Bit Manipulation
Number of Corner Rectangles Array, Matrix, Math
Magic Squares In Grid Array, Matrix, Simulation
Maximum Number of Fish in a Grid Array, Matrix, Depth-First Search
Construct Product Matrix Array, Matrix, Prefix Sum
Maximum Number of Moves in a Grid Array, Matrix, Dynamic Programming
Map of Highest Peak Array, Matrix, Breadth-First Search
Convert an Array Into a 2D Array With Conditions Array, Matrix, Hash Table
Check Knight Tour Configuration Array, Matrix, Depth-First Search
First Completely Painted Row or Column Array, Matrix, Hash Table
Rotating the Box Array, Matrix, Two Pointers
Find All Groups of Farmland Array, Matrix, Depth-First Search
Matrix Block Sum Array, Matrix, Prefix Sum
Spiral Matrix III Array, Matrix, Simulation
Where Will the Ball Fall Array, Matrix, Simulation
Maximum Matrix Sum Array, Matrix, Greedy
Difference Between Ones and Zeros in Row and Column Array, Matrix, Simulation
Find the N-th Value After K Seconds Array, Math, Simulation
Minimum Cost Tree From Leaf Values Array, Dynamic Programming, Stack
The Number of Beautiful Subsets Array, Hash Table, Dynamic Programming
Longest Binary Subsequence Less Than or Equal to K String, Greedy, Dynamic Programming
Number of Ways to Select Buildings String, Dynamic Programming, Prefix Sum
Number of People Aware of a Secret Queue, Dynamic Programming, Simulation
Longest Ideal Subsequence Hash Table, String, Dynamic Programming
Stone Game II Array, Dynamic Programming, Prefix Sum
Predict the Winner Array, Dynamic Programming, Recursion
Count Alternating Subarrays Array, Math, Dynamic Programming
Count Ways To Build Good Strings Dynamic Programming
Longest Arithmetic Subsequence Array, Hash Table, Dynamic Programming
Coin Change II Array, Dynamic Programming
Minimum Impossible OR Array, Bit Manipulation, Brainteaser
Minimum Additions to Make Valid String String, Greedy, Dynamic Programming
Partition String Into Substrings With Values at Most K String, Greedy, Dynamic Programming
Stone Game IX Array, Math, Greedy
Minimum Operations to Make Median of Array Equal to K Array, Greedy, Sorting
Destroy Sequential Targets Array, Hash Table, Counting
Smallest Missing Non-negative Integer After Operations Array, Hash Table, Math
Separate Black and White Balls String, Greedy, Two Pointers
Find the Maximum Number of Marked Indices Array, Two Pointers, Greedy
Maximum Split of Positive Even Integers Math, Greedy
Find Three Consecutive Integers That Sum to a Given Number Math, Simulation
Maximum Consecutive Floors Without Special Floors Array, Sorting, Greedy
Count Collisions on a Road String, Stack, Simulation
Video Stitching Array, Greedy, Dynamic Programming
Eliminate Maximum Number of Monsters Array, Greedy, Sorting
Removing Minimum and Maximum From Array Array, Greedy
Minimum Number of Operations to Move All Balls to Each Box Array, String, Prefix Sum
Minimum Number of Arrows to Burst Balloons Array, Greedy, Sorting
Maximum Number of Removable Characters Array, String, Binary Search
Divide Chocolate Array, Binary Search, Greedy
Successful Pairs of Spells and Potions Array, Binary Search, Sorting
Search a 2D Matrix II Array, Matrix, Binary Search
Find Right Interval Array, Binary Search, Sorting
House Robber IV Array, Binary Search, Greedy
Minimize the Maximum Difference of Pairs Array, Binary Search, Greedy
Maximum Candies Allocated to K Children Array, Binary Search
Peak Index in a Mountain Array Array, Binary Search
H-Index II Array, Binary Search
Find the Smallest Divisor Given a Threshold Array, Binary Search
Maximum Value at a Given Index in a Bounded Array Binary Search, Greedy, Math
Find the Student That Will Replace the Chalk Array, Binary Search, Prefix Sum
Minimum Limit of Balls in a Bag Array, Binary Search
Magnetic Force Between Two Balls Array, Binary Search, Sorting
Minimum Number of Days to Make m Bouquets Array, Binary Search
Capacity to Ship Packages Within D Days Array, Binary Search
Find First and Last Position of Element in Sorted Array Array, Binary Search
Find Minimum in Rotated Sorted Array II Array, Binary Search
Search in Rotated Sorted Array II Array, Binary Search
Minimum Consecutive Cards to Pick Up Array, Hash Table, Sliding Window
Max Consecutive Ones II Array, Sliding Window, Dynamic Programming
Minimum Swaps to Group All 1's Together II Array, Sliding Window
Length of Longest Subarray With at Most K Frequency Array, Hash Table, Sliding Window
Maximum Beauty of an Array After Applying Operation Array, Sliding Window, Sorting
Count Complete Subarrays in an Array Array, Hash Table, Sliding Window
Number of Subarrays with Bounded Maximum Array, Sliding Window, Two Pointers
Count the Number of Good Subarrays Array, Hash Table, Sliding Window
Swap For Longest Repeated Character Substring String, Sliding Window, Hash Table
Replace the Substring for Balanced String String, Sliding Window, Two Pointers
Get Equal Substrings Within Budget String, Sliding Window, Binary Search
Maximize the Confusion of an Exam String, Sliding Window, Prefix Sum
Frequency of the Most Frequent Element Array, Sliding Window, Greedy
K Radius Subarray Averages Array, Sliding Window, Prefix Sum
Maximum Points You Can Obtain from Cards Array, Sliding Window, Prefix Sum
Grumpy Bookstore Owner Array, Sliding Window
Number of Substrings Containing All Three Characters String, Hash Table, Sliding Window
Longest Substring with At Most K Distinct Characters String, Hash Table, Sliding Window
Longest Substring with At Most Two Distinct Characters String, Hash Table, Sliding Window
Sentence Similarity III String, Two Pointers, Array
Watering Plants II Array, Two Pointers, Simulation
Number of Subsequences That Satisfy the Given Sum Condition Array, Two Pointers, Sorting
The k Strongest Values in an Array Array, Two Pointers, Sorting
3Sum With Multiplicity Array, Hash Table, Two Pointers
Most Profit Assigning Work Array, Two Pointers, Greedy
Push Dominoes String, Two Pointers, Dynamic Programming
Longest Mountain in Array Array, Two Pointers, Dynamic Programming
Partition Array Such That Maximum Difference Is K Array, Greedy, Sorting
Sort Transformed Array Array, Two Pointers, Math
Bag of Tokens Array, Two Pointers, Greedy
Max Number of K-Sum Pairs Array, Two Pointers, Hash Table
4Sum Array, Two Pointers, Sorting
Maximum Distance Between a Pair of Values Array, Two Pointers, Binary Search
Sum of Square Numbers Math, Two Pointers, Binary Search
Maximum OR Bit Manipulation, Array, Greedy
Minimum Array End Bit Manipulation, Greedy
Number of Wonderful Substrings Bit Manipulation, Hash Table, String
Bitwise ORs of Subarrays Bit Manipulation, Array, Dynamic Programming
Find the Longest Substring Containing Vowels in Even Counts Bit Manipulation, Hash Table, String
Longest Nice Subarray Bit Manipulation, Array, Sliding Window
UTF-8 Validation Bit Manipulation, Array
Maximum XOR for Each Query Bit Manipulation, Array, Prefix Sum
Count Number of Maximum Bitwise-OR Subsets Bit Manipulation, Backtracking, Enumeration
XOR Queries of a Subarray Bit Manipulation, Array, Prefix Sum
Decode XORed Permutation Bit Manipulation, Array, Brainteaser
Minimize XOR Bit Manipulation, Greedy
Flip String to Monotone Increasing String, Dynamic Programming, Bit Manipulation
Find the Xor-Beauty of Array Bit Manipulation, Array, Math
Maximum XOR After Operations Bit Manipulation, Array, Brainteaser
Longest Subarray With Maximum Bitwise AND Bit Manipulation, Array, Brainteaser
Minimum Number of Operations to Make Array XOR Equal to K Bit Manipulation, Array
Find The Original Array of Prefix Xor Bit Manipulation, Array, Prefix Sum
Bitwise XOR of All Pairings Bit Manipulation, Array, Brainteaser
Minimum Time to Repair Cars Array, Binary Search, Greedy
Maximum Value of an Ordered Triplet I Array, Math, Prefix Sum
Super Ugly Number Dynamic Programming, Math, Heap
Minimum Moves to Reach Target Score Math, Greedy
The kth Factor of n Math, Number Theory
Integer Replacement Bit Manipulation, Greedy, Dynamic Programming
Clumsy Factorial Math, Stack, Simulation
Reordered Power of 2 Math, Counting, Enumeration
Minimum Operations to Reduce an Integer to 0 Bit Manipulation, Greedy, Dynamic Programming
Closest Divisors Math, Number Theory
Maximum Product After K Increments Array, Greedy, Heap
Prime Subtraction Operation Array, Math, Greedy
Minimum Number of Operations to Make Array Empty Hash Table, Greedy, Counting
Smallest Value After Replacing With Sum of Prime Factors Math, Number Theory, Simulation
Number of Zero-Filled Subarrays Array, Math, Counting
4Sum II Hash Table, Array, Counting
Find Players With Zero or One Losses Hash Table, Array, Sorting
Minimum Area Rectangle Hash Table, Array, Geometry
Number of Boomerangs Hash Table, Math, Array
Group the People Given the Group Size They Belong To Hash Table, Array, Greedy
Optimal Partition of String Hash Table, String, Greedy
Count Number of Bad Pairs Hash Table, Array, Counting
Determine if Two Strings Are Close Hash Table, String, Counting
Equal Row and Column Pairs Hash Table, Matrix, Simulation
Brick Wall Hash Table, Array, Counting
Smallest String With Swaps Union Find, Hash Table, String
Number of Pairs of Interchangeable Rectangles Array, Hash Table, Math
Count Nice Pairs in an Array Array, Hash Table, Math
Maximum Size Subarray Sum Equals k Array, Hash Table, Prefix Sum
Longest Well-Performing Interval Array, Hash Table, Prefix Sum
Subarray Sums Divisible by K Array, Hash Table, Prefix Sum
Maximum Number of Integers to Choose From a Range I Hash Table, Greedy, Binary Search
Short Encoding of Words String, Trie, Hash Table
Replace Words String, Trie, Hash Table
Longest Word in Dictionary String, Trie, Hash Table
Word Subsets String, Hash Table, Counting
Number of Good Ways to Split a String String, Hash Table, Prefix Sum
Minimum Length of String After Deleting Similar Ends String, Two Pointers
Can Convert String in K Moves String, Hash Table, Greedy
Longest Substring With At Least K Repeating Characters String, Sliding Window, Divide and Conquer
Maximum Number of Occurrences of a Substring String, Sliding Window, Hash Table
Number of Ways to Split a String String, Math, Counting
Minimum Number of Frogs Croaking String, Greedy, Counting
Check If a String Can Break Another String String, Greedy, Sorting
Count Substrings That Differ by One Character String, Dynamic Programming
Maximum Length of a Concatenated String With Unique Characters String, Bit Manipulation, Backtracking
Count Words Obtained After Adding a Letter String, Bit Manipulation, Hash Table
Longest Word in Dictionary Through Deleting String, Two Pointers, Sorting
Number of Matching Subsequences String, Two Pointers, Binary Search
Find and Replace Pattern String, Hash Table
Count Triplets With Sum Smaller Than X Array, Two Pointers, Sorting
Kth Smallest Element Array, Sorting, Quickselect
Maximum Index Array, Two Pointers
Rearrange Array in Max/Min Form Array, Two Pointers
Subarray With Given Sum Array, Sliding Window, Two Pointers
Longest Subarray With Sum Zero Array, Hash Table, Prefix Sum
Minimum Swaps to Sort Array, Sorting, Graph
Count Inversions Array, Divide and Conquer, Fenwick Tree
Divide Array Into Arrays With Max Difference Array, Greedy, Sorting
Count Number of Teams Array, Dynamic Programming
Uncrossed Lines Array, Dynamic Programming
Minimum ASCII Delete Sum for Two Strings String, Dynamic Programming
Longest Palindromic Subsequence String, Dynamic Programming
Unique Binary Search Trees Dynamic Programming, Math
Domino and Tromino Tiling Dynamic Programming
Paint House Array, Dynamic Programming
Paint Fence Dynamic Programming
Minimum Operations to Make Array Equal Math
Reach a Number Math, Binary Search
Smallest Value of the Rearranged Number Math, Sorting
Check if Number is a Sum of Powers of Three Math, Number Theory
Number of Steps to Reduce a Number in Binary Representation to One String, Bit Manipulation, Simulation
Find Original Array From Doubled Array Array, Greedy, Sorting
K-diff Pairs in an Array Array, Hash Table
Non-decreasing Array Array, Greedy
Minimum Moves to Equal Array Elements II Array, Math, Sorting
Minimum Moves to Equal Array Elements Array, Math
Word Search Array, String, Backtracking
Pacific Atlantic Water Flow Array, Depth-First Search, Breadth-First Search
Snakes and Ladders Array, Breadth-First Search, Matrix
Minimum Genetic Mutation Hash Table, String, Breadth-First Search
Jump Game III Array, Depth-First Search, Breadth-First Search
Count Unreachable Pairs of Nodes in an Undirected Graph Depth-First Search, Breadth-First Search, Union Find
Maximum Total Importance of Roads Graph, Greedy, Sorting
Find Closest Node to Given Two Nodes Depth-First Search, Graph
Maximal Network Rank Graph
Path With Minimum Effort Array, Binary Search, Depth-First Search
Time Needed to Inform All Employees Tree, Depth-First Search, Breadth-First Search
Reorder Routes to Make All Paths Lead to the City Zero Depth-First Search, Breadth-First Search, Graph
Possible Bipartition Depth-First Search, Breadth-First Search, Union Find
Minimum Height Trees Depth-First Search, Breadth-First Search, Graph
Detect Cycles in 2D Grid Array, Depth-First Search, Breadth-First Search
Number of Distinct Islands Array, Hash Table, Depth-First Search
Shortest Bridge Array, Depth-First Search, Breadth-First Search
The Earliest Moment When Everyone Become Friends Array, Union Find, Sorting
Number of Operations to Make Network Connected Depth-First Search, Breadth-First Search, Union Find
Count Sub Islands Array, Depth-First Search, Breadth-First Search
As Far from Land as Possible Array, Dynamic Programming, Breadth-First Search
Shortest Path in Binary Matrix Array, Breadth-First Search, Matrix
Number of Enclaves Array, Depth-First Search, Breadth-First Search
Minimum Number of Vertices to Reach All Nodes Graph
Find Eventual Safe States Depth-First Search, Breadth-First Search, Graph
All Paths From Source to Target Backtracking, Depth-First Search, Breadth-First Search
Keys and Rooms Depth-First Search, Breadth-First Search, Graph
Is Graph Bipartite? Depth-First Search, Breadth-First Search, Union Find
Graph Valid Tree Depth-First Search, Breadth-First Search, Union Find
Number of Connected Components in an Undirected Graph Depth-First Search, Breadth-First Search, Union Find
Rotate Function Array, Math, Dynamic Programming
Nth Digit Math, Binary Search
Bulb Switcher Math, Brainteaser
Count Triplets That Can Form Two Arrays of Equal XOR Array, Hash Table, Math
Divide Two Integers Math, Bit Manipulation
Concatenation of Consecutive Binary Numbers Math, Bit Manipulation, Simulation
Maximum Product of Word Lengths Array, String, Bit Manipulation
Sort Integers by The Power Value Dynamic Programming, Memoization, Sorting
Minimum Flips to Make a OR b Equal to c Bit Manipulation
Gray Code Math, Backtracking, Bit Manipulation
Maximum XOR of Two Numbers in an Array Array, Hash Table, Bit Manipulation
Sum of Two Integers Math, Bit Manipulation
Bitwise AND of Numbers Range Bit Manipulation
Total Hamming Distance Array, Math, Bit Manipulation
Single Number III Array, Bit Manipulation
Single Number II Array, Bit Manipulation
Buildings With an Ocean View Array, Stack, Monotonic Stack
Minimum Insertions to Balance a Parentheses String String, Stack, Greedy
Remove All Adjacent Duplicates in String II String, Stack
The Number of Weak Characters in the Game Array, Greedy, Sorting
Maximum Score From Removing Substrings String, Stack, Greedy
Minimum Number of Swaps to Make the String Balanced String, Stack, Greedy
Remove All Occurrences of a Substring String, Stack, Simulation
Max Chunks To Make Sorted Array, Stack, Greedy
Sum of Subarray Ranges Array, Stack, Monotonic Stack
Removing Stars From a String String, Stack, Simulation
Dota2 Senate String, Greedy, Queue
Reveal Cards In Increasing Order Array, Queue, Sorting
Reverse Substrings Between Each Pair of Parentheses String, Stack
Basic Calculator II Math, String, Stack
Validate Stack Sequences Array, Stack, Simulation
Next Greater Element III Math, Two Pointers, String
Maximum Width Ramp Array, Stack, Monotonic Stack
132 Pattern Array, Binary Search, Stack
Sum of Subarray Minimums Array, Dynamic Programming, Stack
Build an Array With Stack Operations Array, Stack, Simulation
Check If Word Is Valid After Substitutions String, Stack
Score of Parentheses String, Stack
Minimum Remove to Make Valid Parentheses String, Stack
Minimum Add to Make Parentheses Valid String, Stack, Greedy
Minimum Number of Platforms Array, Greedy, Sorting
Find K Closest Elements Array, Two Pointers, Binary Search
Kth Smallest Element in a Sorted Matrix Array, Binary Search, Sorting
Top K Frequent Words Array, Hash Table, String
K Closest Points to Origin Array, Math, Divide and Conquer
Partition Array into Disjoint Intervals Array, Greedy
Minimum Time to Make Rope Colorful Array, String, Dynamic Programming
Remove Duplicate Letters String, Stack, Greedy
Monotone Increasing Digits Math, Greedy
Maximum Swap Math, Greedy
Valid Triangle Number Array, Two Pointers, Binary Search
Rearrange Array Elements by Sign Array, Two Pointers, Simulation
Maximum Number of Coins You Can Get Array, Math, Greedy
Largest Number Array, String, Greedy
Maximum Ice Cream Bars Array, Greedy, Sorting
Remove Covered Intervals Array, Greedy, Sorting
Minimum Number of Steps to Make Two Strings Anagram Hash Table, String, Counting
Minimum Deletions to Make Character Frequencies Unique String, Hash Table, Greedy
Reduce Array Size to The Half Array, Hash Table, Greedy
Queue Reconstruction by Height Array, Greedy, Sorting
Two City Scheduling Array, Greedy, Sorting
Knight Dialer Dynamic Programming
2 Keys Keyboard Math, Dynamic Programming
Maximum Length of Pair Chain Array, Dynamic Programming, Greedy
Longest Turbulent Subarray Array, Dynamic Programming, Sliding Window
Number of Dice Rolls With Target Sum Dynamic Programming
Best Sightseeing Pair Array, Dynamic Programming
Maximum Sum Circular Subarray Array, Divide and Conquer, Dynamic Programming
Minimum Cost For Tickets Array, Dynamic Programming
Longest String Chain Array, Hash Table, Two Pointers
Combination Sum IV Array, Dynamic Programming
Ones and Zeroes Array, String, Dynamic Programming
Last Stone Weight II Array, Dynamic Programming
Stone Game Array, Math, Dynamic Programming
Count Numbers with Unique Digits Math, Dynamic Programming, Backtracking
Ugly Number II Hash Table, Math, Dynamic Programming
Integer Break Math, Dynamic Programming
Perfect Squares Math, Dynamic Programming, Breadth-First Search
Triangle Array, Dynamic Programming
Minimum Falling Path Sum Array, Dynamic Programming, Matrix
Interleaving String String, Dynamic Programming
Delete Operation for Two Strings String, Dynamic Programming
Count Sorted Vowel Strings Dynamic Programming, Math, Combinatorics
Arithmetic Slices Array, Dynamic Programming
Wiggle Subsequence Array, Dynamic Programming, Greedy
Number of Longest Increasing Subsequence Array, Dynamic Programming, Binary Indexed Tree
Longest Arithmetic Subsequence of Given Difference Array, Hash Table, Dynamic Programming
Maximum Length of Repeated Subarray Array, Binary Search, Dynamic Programming
Best Time to Buy and Sell Stock with Transaction Fee Array, Dynamic Programming, Greedy
Best Time to Buy and Sell Stock with Cooldown Array, Dynamic Programming
Delete and Earn Array, Hash Table, Dynamic Programming
Valid Sudoku Array, Hash Table, Matrix
Count Servers that Communicate Array, Depth-First Search, Breadth-First Search
Number of Closed Islands Array, Depth-First Search, Breadth-First Search
Surrounded Regions Array, Depth-First Search, Breadth-First Search
Game of Life Array, Matrix, Simulation
Count Square Submatrices with All Ones Array, Dynamic Programming, Matrix
Maximal Square Array, Dynamic Programming, Matrix
Unique Paths II Array, Dynamic Programming, Matrix
Minimum Path Sum Array, Dynamic Programming, Matrix
Sort the Matrix Diagonally Array, Sorting, Matrix
Max Increase to Keep City Skyline Array, Greedy, Matrix
Diagonal Traverse Array, Matrix, Simulation
Spiral Matrix II Array, Matrix, Simulation
Remove Duplicates from Sorted Array II Array, Two Pointers
Count Number of Nice Subarrays Array, Hash Table, Math
Binary Subarrays With Sum Array, Hash Table, Sliding Window
Maximum Erasure Value Array, Hash Table, Sliding Window
Minimum Operations to Reduce X to Zero Array, Hash Table, Binary Search
Longest Subarray of 1's After Deleting One Element Array, Dynamic Programming, Sliding Window
Continuous Subarray Sum Array, Hash Table, Math
Contiguous Array Array, Hash Table, Prefix Sum
Subarray Product Less Than K Array, Sliding Window, Binary Search
Number of Sub-arrays of Size K and Average Greater than or Equal to Threshold Array, Sliding Window
Maximum Number of Vowels in a Substring of Given Length String, Sliding Window
Custom Sort String Hash Table, String, Sorting
Valid Parenthesis String String, Dynamic Programming, Stack
String Compression Two Pointers, String
Count and Say String, Simulation
Reverse Words in a String Two Pointers, String
Majority Element II Array, Hash Table, Sorting
Increasing Triplet Subsequence Array, Greedy
H-Index Array, Sorting, Counting Sort
Shortest Unsorted Continuous Subarray Array, Two Pointers, Sorting
Next Permutation Array, Two Pointers
Find All Duplicates in an Array Array, Hash Table
Integer to Roman Hash Table, Math, String
Factorial Trailing Zeroes Math
Count Primes Math, Sieve of Eratosthenes
Reverse Integer Math

Hard (139)

Count Ways to Make Array With Product Array, Math, Dynamic Programming
Count the Number of Ideal Arrays Math, Dynamic Programming, Combinatorics
Number of Ways to Rearrange Sticks With K Sticks Visible Math, Dynamic Programming, Combinatorics
The Number of Good Subsets Array, Math, Dynamic Programming
Number of Ways to Reorder Array to Get Same BST Array, Math, Divide and Conquer
Make Array Strictly Increasing Array, Binary Search, Dynamic Programming
Odd Even Jump Array, Dynamic Programming, Stack
Maximum Number of Events That Can Be Attended II Array, Binary Search, Dynamic Programming
Minimum Replacements to Sort the Array Array, Math, Greedy
Create Sorted Array Through Instructions Array, Binary Search, Divide and Conquer
Painting the Walls Array, Dynamic Programming
Reverse Pairs Array, Binary Search, Divide and Conquer
Number of Ways to Separate Numbers String, Dynamic Programming, Suffix Array
Painting a Grid With Three Different Colors Dynamic Programming, Bitmask
Minimum Incompatibility Array, Dynamic Programming, Bit Manipulation
Number of Distinct Roll Sequences Dynamic Programming, Memoization
Form Largest Integer With Digits That Add up to Target Array, String, Dynamic Programming
Build Array Where You Can Find The Maximum Exactly K Comparisons Dynamic Programming, Prefix Sum
Stone Game VIII Array, Math, Dynamic Programming
Allocate Mailboxes Array, Math, Dynamic Programming
Constrained Subsequence Sum Array, Dynamic Programming, Queue
Restore the Array String, Dynamic Programming
Count All Valid Pickup and Delivery Options Math, Dynamic Programming, Combinatorics
Maximum Height by Stacking Cuboids Array, Dynamic Programming, Sorting
Cherry Pickup II Array, Dynamic Programming, Matrix
Strange Printer String, Dynamic Programming
Number of Ways to Stay in the Same Place After Some Steps Dynamic Programming
Maximum Value of K Coins From Piles Array, Dynamic Programming, Prefix Sum
Count Special Integers Math, Dynamic Programming, Combinatorics
Number of Great Partitions Array, Dynamic Programming
Minimum Cost to Split an Array Array, Hash Table, Dynamic Programming
Paths in Matrix Whose Sum Is Divisible by K Array, Dynamic Programming, Matrix
Special Binary String String, Recursion, Divide and Conquer
Count Different Palindromic Subsequences String, Dynamic Programming
Smallest K-Length Subsequence With Occurrences of a Letter String, Stack, Greedy
Valid Palindrome III String, Dynamic Programming
Count Anagrams Hash Table, Math, String
String Compression II String, Dynamic Programming
Apply Operations to Maximize Score Array, Math, Stack
Meeting Rooms III Array, Sorting, Simulation
Smallest Range Covering Elements from K Lists Array, Hash Table, Greedy
Minimize Deviation in Array Array, Greedy, Heap (Priority Queue)
Maximum Performance of a Team Array, Greedy, Sorting
Construct Target Array With Multiple Sums Array, Heap (Priority Queue), Math
Minimum Number of Operations to Make Array Continuous Array, Hash Table, Binary Search
Put Marbles in Bags Array, Greedy, Sorting
Minimum Time to Visit a Cell In a Grid Array, Matrix, Graph
Minimum Number of Days to Disconnect Island Array, Matrix, Depth-First Search
Number of Increasing Paths in a Grid Array, Matrix, Dynamic Programming
Checking Existence of Edge Length Limited Paths Array, Union Find, Graph
Find All People With Secret Graph, Union Find, Depth-First Search
Minimum Obstacle Removal to Reach Corner Array, Matrix, Graph
Number of Good Paths Array, Tree, Graph
Largest Component Size by Common Factor Array, Math, Union Find
Critical Connections in a Network Graph, Depth-First Search, Biconnected Component
Bus Routes Array, Hash Table, Breadth-First Search
Number of Restricted Paths From First to Last Node Graph, Dynamic Programming, Shortest Path
Sliding Puzzle Array, Matrix, Breadth-First Search
Jump Game IV Array, Hash Table, Breadth-First Search
Trapping Rain Water II Array, Matrix, Heap (Priority Queue)
Escape the Spreading Fire Array, Matrix, Binary Search
Grid Illumination Array, Hash Table, Matrix
Shortest Distance from All Buildings Array, Matrix, Breadth-First Search
Minimum Moves to Spread Stones Over Grid Array, Matrix, Dynamic Programming
Making A Large Island Array, Matrix, Depth-First Search
Unique Paths III Array, Matrix, Backtracking
Number of Submatrices That Sum to Target Array, Matrix, Hash Table
Longest Increasing Path in a Matrix Array, Matrix, Dynamic Programming
Maximal Rectangle Array, Matrix, Stack
Minimum Difficulty of a Job Schedule Array, Dynamic Programming
Minimum Cost to Cut a Stick Array, Dynamic Programming, Sorting
Minimum White Tiles After Covering With Carpets String, Dynamic Programming, Prefix Sum
Maximum Number of Groups With Increasing Length Array, Greedy, Sorting
Number of Ways to Earn Points Array, Dynamic Programming
Scramble String String, Dynamic Programming
Number of Music Playlists Math, Dynamic Programming, Combinatorics
Profitable Schemes Array, Dynamic Programming
Distinct Subsequences II String, Dynamic Programming
Cherry Pickup Array, Matrix, Dynamic Programming
Number of Ways to Paint N × 3 Grid Dynamic Programming
Tallest Billboard Array, Dynamic Programming
Best Time to Buy and Sell Stock IV Array, Dynamic Programming
Burst Balloons Array, Dynamic Programming
Frog Jump Array, Hash Table, Dynamic Programming
Minimum Falling Path Sum II Array, Matrix, Dynamic Programming
Dungeon Game Array, Matrix, Dynamic Programming
Minimum Time to Complete All Tasks Array, Greedy, Sorting
Minimum Number of Refueling Stops Array, Greedy, Dynamic Programming
IPO Array, Greedy, Sorting
Minimum Number of Taps to Open to Water a Garden Array, Greedy, Dynamic Programming
Maximum Number of Tasks You Can Assign Array, Binary Search, Greedy
Find the Kth Smallest Sum of a Matrix With Sorted Rows Array, Matrix, Binary Search
Russian Doll Envelopes Array, Binary Search, Dynamic Programming
Maximum Running Time of N Computers Array, Binary Search, Greedy
Minimum Time to Complete Trips Array, Binary Search
Kth Smallest Number in Multiplication Table Math, Binary Search
Split Array Largest Sum Array, Binary Search, Greedy
Minimum Number of Flips to Make the Binary String Alternating String, Sliding Window, Dynamic Programming
Take K of Each Character From Left and Right String, Hash Table, Sliding Window
Minimum Number of K Consecutive Bit Flips Array, Sliding Window, Prefix Sum
Shortest Subarray with Sum at Least K Array, Prefix Sum, Sliding Window
Count Subarrays With Fixed Bounds Array, Sliding Window, Two Pointers
Maximum Number of Robots Within Budget Array, Sliding Window, Two Pointers
Minimum Window Subsequence String, Two Pointers, Dynamic Programming
Minimum Number of Moves to Make Palindrome String, Two Pointers, Greedy
Find K-th Smallest Pair Distance Array, Two Pointers, Binary Search
Subarrays with K Different Integers Array, Hash Table, Sliding Window
Shortest Path Visiting All Nodes Bit Manipulation, Breadth-First Search, Graph
Count the Number of Square-Free Subsets Bit Manipulation, Dynamic Programming, Bitmask
Maximum AND Sum of Array Bit Manipulation, Dynamic Programming, Bitmask
Find Subarray With Bitwise OR Closest to K Bit Manipulation, Array, Binary Search
Minimum One Bit Operations to Make Integers Zero Bit Manipulation, Math, Dynamic Programming
Smallest Good Base Math, Binary Search, Number Theory
Number of Digit One Math, Digit DP, Recursion
Preimage Size of Factorial Zeroes Function Math, Binary Search, Number Theory
Nth Magical Number Math, Binary Search, Number Theory
Largest Multiple of Three Array, Greedy, Dynamic Programming
Count of Range Sum Fenwick Tree, Divide and Conquer, Prefix Sum
Substring with Concatenation of All Words Hash Table, String, Sliding Window
Max Points on a Line Hash Table, Math, Geometry
Longest Happy Prefix String, KMP, Rolling Hash
Count Unique Characters of All Substrings of a Given String String, Hash Table, Counting
Shortest Palindrome String, KMP, Rolling Hash
Max Value of Equation Array, Monotonic Queue, Sliding Window
Count of Smaller Numbers After Self Array, Fenwick Tree, Divide and Conquer
Stone Game IV Math, Dynamic Programming, Game Theory
Stone Game III Array, Dynamic Programming, Game Theory
Palindrome Partitioning II String, Dynamic Programming
Wildcard Matching String, Dynamic Programming, Greedy
Distinct Subsequences String, Dynamic Programming
Max Dot Product Between Two Subsequences Array, Dynamic Programming
Minimum Insertion Steps to Make a String Palindrome String, Dynamic Programming
Swim in Rising Water Array, Binary Search, Depth-First Search
Word Ladder Hash Table, String, Breadth-First Search
Longest Cycle in a Graph Depth-First Search, Graph, Topological Sort
Number of Visible People in a Queue Array, Stack, Monotonic Stack
Longest Valid Parentheses String, Dynamic Programming, Stack
Count Vowels Permutation Dynamic Programming
Best Time to Buy and Sell Stock III Array, Dynamic Programming

Topics Amazon asks most

Arrays 552 problems
Strings 238 problems
Math 185 problems
Hash Table 171 problems
Dynamic Programming 166 problems
Greedy 144 problems
Sorting 136 problems
Matrix 93 problems
Two Pointers 89 problems
Simulation 78 problems
Binary Search 77 problems
Bit Manipulation 77 problems