Skip to main content

2206. Divide Array Into Equal Pairs

題目​

完整題目

You are given an integer array nums consisting of 2 * n integers.

You need to divide nums into n pairs such that:

Each element belongs to exactly one pair. The elements present in a pair are equal. Return true if nums can be divided into n pairs, otherwise return false.

Example 1

Input: nums = [3,2,3,2,2,2]
Output: true
Explanation:
There are 6 elements in nums, so they should be divided into 6 / 2 = 3 pairs.
If nums is divided into the pairs (2, 2), (3, 3), and (2, 2), it will satisfy all the conditions.

Example 2

Input: nums = [1,2,3,4]
Output: false
Explanation:
There is no way to divide nums into 4 / 2 = 2 pairs such that the pairs satisfy every condition.

Constraints

  • nums.length==2∗nnums.length == 2 * n
  • 1≤n≤5001 \le n \le 500
  • 1≤nums[i]≤5001 \le nums[i] \le 500

題目難易度​

Easy

解題想法​

題目的重點在於同一個 element 可不可以找到一對的，所以我們只需要統計每個數字出現的次數，並看是否可以被 2 整除即可。

初試​

  • Time Complexity: O(n)O(n)
  • Space Complexity: O(n)O(n)
/**
 * @param {number[]} nums
 * @return {boolean}
 */
var divideArray = function (nums) {
  const pair = new Map();

  for (const num of nums) {
    pair.set(num, pair.has(num) ? pair.get(num) + 1 : 1);
  }

  let ans = true;
  pair.forEach((value) => {
    if (value % 2 !== 0) ans = false;
  });

  return ans;
};