Maximum Number of Pairs in Array — LeetCode 2341 Python Solution

The problem

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.

Example

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].

Python solution

class Solution:
    def numberOfPairs(self, nums: List[int]) -> List[int]:
        cnt = Counter(nums)
        s = sum(v // 2 for v in cnt.values())
        return [s, len(nums) - s * 2]

Complexity

Pattern: Hash Map

Trade memory for time: remember what you have seen so the second pass never happens. LeetCode 2341. Maximum Number of Pairs in Array is filed here on both counts: the reference solution below belongs to the algorithm family this hub collects, and LeetCode tags it Hash Table and Counting.

The hash map guide has the Python template for the pattern and the 709 LeetCode problems that use it.

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