Maximum Number of Pairs in Array

You are given a 0-indexed integer array nums. In one operation, you may do the following:

Choose two integers in nums that are equal. Remove both integers from nums, forming a pair. The operation is done on nums as many times as possible.

Return a 0-indexed integer array answer of size 2 where answer[0] is the number of pairs that are formed and answer[1] is the number of leftover integers in nums after doing the operation as many times as possible.

Example 1:

Input: nums = [1,3,2,1,3,2,2]
Output: [3,1]
Explanation:
Form a pair with nums[0] and nums[3] and remove them from nums. Now, nums = [3,2,3,2,2].
Form a pair with nums[0] and nums[2] and remove them from nums. Now, nums = [2,2,2].
Form a pair with nums[0] and nums[1] and remove them from nums. Now, nums = [2].
No more pairs can be formed. A total of 3 pairs have been formed, and there is 1 number leftover in nums.

Example 2:

Input: nums = [1,1]
Output: [1,0]
Explanation: Form a pair with nums[0] and nums[1] and remove them from nums. Now, nums = [].
No more pairs can be formed. A total of 1 pair has been formed, and there are 0 numbers leftover in nums.

Example 3:

Input: nums = [0]
Output: [0,1]
Explanation: No pairs can be formed, and there is 1 number leftover in nums.

Solution

class Solution:
    def numberOfPairs(self, nums: List[int]) -> List[int]:
        pairs = 0
        rem = 0
        dic = dict()
        for n in nums:
            dic[n] = dic.get(n, 0) + 1
        for v, k in dic.items():
            pairs += k // 2
            rem += k % 2
        return [pairs, rem]