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Coding problem · Easy · Language Idioms

Leaderboard Sorting with usort and <=>

Easy Language practicals Seen at Booking.com, Automattic, Shopify

You receive players as associative arrays: ['name' => 'Ana', 'score' => 90, 'timeSec' => 61].

Return the player names ranked by:

  1. score descending,
  2. then timeSec ascending (faster wins ties),
  3. then name ascending.

Example 1

Input: players = [Ana 90 61, Bo 95 70, Cy 90 55]
Output: ["Bo","Cy","Ana"]

Hints

Hint 1

usort with a comparator returning <=> of two arrays compares element by element.

Hint 2

Swap $a/$b on one side for descending order.

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Solution and explanation

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Time O(n log n) · Space O(n)

The spaceship operator <=> compares arrays element by element, so [$b['score'], $a['timeSec'], $a['name']] <=> [$a['score'], $b['timeSec'], $b['name']] expresses "score descending, then time ascending, then name ascending" in one line. array_column then extracts the names.

Since PHP 8.0 usort is stable, but relying on an explicit final tie-breaker keeps results deterministic everywhere.

Reference solution

<?php

function rankPlayers(array $players): array
{
    usort(
        $players,
        fn(array $a, array $b): int => [$b['score'], $a['timeSec'], $a['name']] <=> [$a['score'], $b['timeSec'], $b['name']]
    );
    return array_column($players, 'name');
}

Common mistakes

  • Returning a boolean from the comparator ($a > $b) — it must return an int.
  • Using sort() on associative arrays and losing structure.

Follow-up questions

  • Sort a list of objects with readonly properties instead of arrays.
  • Rank with ties sharing a position (dense ranking).