leetcode 454. 4Sum II

题目描述

代码：

class Solution {
public:int fourSumCount(vector<int>& nums1, vector<int>& nums2, vector<int>& nums3, vector<int>& nums4) {unordered_map<int,int> table;int temp =0;for(auto n1:nums1){for(auto n2:nums2){temp = n1+n2;if(table.contains(temp))table[temp]++;elsetable[temp]=1;}}int res = 0;for(auto n3:nums3){for(auto n4:nums4){temp = n3+n4;if(table.contains(-temp))res += table[-temp];}}return res;}
};