#2341 - Maximum Number of Pairs in Array

Easy • View on LeetCode • View on GitHub

Problem Description

You are given a 0-indexed integer array nums. In one operation, you may do the following:

Choose two integers in nums that are equal.
Remove both integers from nums, forming a pair.

The operation is done on nums as many times as possible.

Return a 0-indexed integer array answer of size 2 where answer[0] is the number of pairs that are formed and answer[1] is the number of leftover integers in nums after doing the operation as many times as possible.

Solution

/**
 * @param {number[]} nums
 * @return {number[]}
 */
var numberOfPairs = function(nums) {
  const frequency = new Map();
  let pairs = 0;

  for (const num of nums) {
    frequency.set(num, (frequency.get(num) || 0) + 1);
    if (frequency.get(num) === 2) {
      pairs++;
      frequency.set(num, 0);
    }
  }

  const leftovers = nums.length - pairs * 2;
  return [pairs, leftovers];
};