The Leaderboard Shuffle — Java Bug Hunt

Briefing

Inspired by the leaderboard-flicker tickets every game studio collects: players with equal scores swap places on every refresh. Ties must preserve the order they arrived in (stable sort) — but someone "helpfully" added an alphabetical tiebreak.

Leaderboard.java sorts by score, descending, stable.

Bug report

BUG-FLICKER · Reported by: live-ops

sortByScore(names, scores) -> names sorted by score DESC:

• equal scores keep their ORIGINAL relative order (arrival order)
• no other tiebreak, alphabetical or otherwise

Observed: "zoe" reached 50 points before "amy", but every refresh shows amy above zoe — the tiebreak reorders them.

Logs

[board] tie at 50: zoe (first) rendered below amy

The code as shipped

Leaderboard.java (editable)

import java.util.*;

class Leaderboard {
    static String[] sortByScore(String[] names, int[] scores) {
        Integer[] idx = new Integer[names.length];
        for (int i = 0; i < idx.length; i++) idx[i] = i;
        Arrays.sort(idx, new Comparator<Integer>() {
            public int compare(Integer a, Integer b) {
                if (scores[b] != scores[a]) return scores[b] - scores[a];
                return names[a].compareTo(names[b]);
            }
        });
        String[] out = new String[names.length];
        for (int i = 0; i < out.length; i++) out[i] = names[idx[i]];
        return out;
    }
}