LeetCode-in-Java

2206. Divide Array Into Equal Pairs

Easy

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 * n
• 1 <= n <= 500
• 1 <= nums[i] <= 500

Solution

public class Solution {
    public boolean divideArray(int[] nums) {
        int[] freq = new int[501];
        for (int num : nums) {
            ++freq[num];
        }
        for (int f : freq) {
            if (f % 2 != 0) {
                return false;
            }
        }
        return true;
    }
}

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