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2206. Divide Array into Equal Pairs

EasyOpen on LeetCode Problem statement

Problem Statement

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

Java — hashset

class Solution {
    public boolean divideArray(int[] nums) {
        Set<Integer> lone = new HashSet<>();
        for (int i : nums)
            if (lone.contains(i))
                lone.remove(i);
            else
                lone.add(i);
        return lone.isEmpty();
    }
}

Java

class Solution {
    public boolean divideArray(int[] nums) {
        Set<Integer> lone = new HashSet<>();
        for(int i: nums){
            if(lone.contains(i))
                lone.remove(i);
            else lone.add(i);
        }
        return lone.isEmpty();
    }
}