2308. Divide Array Into Equal Pairs¶

LeetCode Problem View on GitHub

2308. 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¶

class Solution {
    public boolean divideArray(int[] nums) {
        HashSet<Integer> set = new HashSet<>();
        int freq[] = new int[501];
        for (int ele : nums) {
            set.add(ele);
            freq[ele]++;
        }
        for (int ele : set) {
            if (freq[ele] % 2 == 1) return false;
        }
        return true;
    }
}

Complexity Analysis¶

• Time Complexity: O(?)
• Space Complexity: O(?)

Approach¶

Detailed explanation of the approach will be added here