1679. Max Number of K-Sum Pairs

leetcode.com/problems/max-number-of-k-sum-pairs/

Max Number of K-Sum Pairs - LeetCode

from collections import Counter

class Solution(object):
    def maxOperations(self, nums, k):

        dic = Counter(nums)
        ans = 0
        for n in nums:
            if k - n in dic:
                if n == k - n:
                    if dic[n] >= 2:
                        dic[n] -= 2
                        ans += 1
                elif dic[n] > 0 and dic[k - n] > 0:
                    dic[n] -= 1
                    dic[k - n] -= 1
                    ans += 1
        return ans

leetcode.com/problems/max-number-of-k-sum-pairs/discuss/1022728/Python-using-dict-O(n)-easy-to-understand-clean

collections.defaultdict

excelsior-cjh.tistory.com/95

collections 모듈 - defaultdict