LeetCode 2206. Divide Array Into Equal Pairs

Question

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

 

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Solution

Python

class Solution:
    def divideArray(self, nums: List[int]) -> bool:
        pairs = len(nums) / 2
        count = 0
        dict_nums = {}
        for i in nums:
            if i in dict_nums.keys():
                dict_nums[i] += 1
            else:
                dict_nums[i] = 1

        for k in dict_nums.keys():
            if dict_nums[k] % 2 == 1:
                return False
            else:
                count += dict_nums[k]
        if count % pairs == 0:
            return True
        return False

Java