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Easytreetraversalqueue

~45s

Structure behind level-order traversal

Which data structure does a level-order (breadth-first) traversal of a binary tree rely on?

Show the answer and the worked solution

Correct answer: C.

A queue

Worked solution

  1. Level-order visits all nodes at depth d before any node at depth d + 1.
  2. Removing a node and adding its children keeps that order, because children join behind everything already waiting.
  3. A queue is exactly that discipline — first in, first out — whereas a stack would reverse the order and produce a depth-first walk instead.

Answer: A queue.

The idea

Breadth-first anything — tree levels, shortest paths in an unweighted graph — is a queue. Depth-first anything is a stack, whether explicit or the recursion stack.

Shortcut. Nodes must leave in the order they were discovered, level by level, which is first in, first out; a heap orders by key and a hash table has no order, so a queue.

Common trap. "A stack" is the usual tool for tree traversals through recursion, but last in, first out dives deep and produces a depth-first order.

Data Structures & Algorithms

7 of 40

Level

Easy

Target time

~45s

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Structure behind level-order traversal — Aptitude Question

Structure behind level-order traversal: Which data structure does a level-order (breadth-first) traversal of a… Answer and worked solution on CodeKairo.

Question

Which data structure does a level-order (breadth-first) traversal of a binary tree rely on?

Options

  1. A hash table
  2. A min-heap
  3. A queue
  4. A stack
Show the answer and the worked solution

Correct answer: C. A queue

Worked solution

  1. Level-order visits all nodes at depth d before any node at depth d + 1.
  2. Removing a node and adding its children keeps that order, because children join behind everything already waiting.
  3. A queue is exactly that discipline — first in, first out — whereas a stack would reverse the order and produce a depth-first walk instead.

Answer: A queue.

The idea

Breadth-first anything — tree levels, shortest paths in an unweighted graph — is a queue. Depth-first anything is a stack, whether explicit or the recursion stack.

Shortcut. Nodes must leave in the order they were discovered, level by level, which is first in, first out; a heap orders by key and a hash table has no order, so a queue.

Common trap. "A stack" is the usual tool for tree traversals through recursion, but last in, first out dives deep and produces a depth-first order.

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