4 Values whose Sum is 0 UVA - 1152

比较简单的一道题目，对于序列A和B，统计出二者中所有的元素之和，并且记录在数组sum中，然后对于序列C和D中的任意的元素之和t，找出sum中-t的个数并且统计。最后将结果输出即可，具体实现见如下代码：

#include<iostream>
#include<vector>
#include<string>
#include<set>
#include<stack>
#include<queue>
#include<map>
#include<algorithm>
#include<cmath>
#include<iomanip>
#include<cstring>
#include<sstream>
#include<cstdio>
#include<deque>
#include<functional>
using namespace std;

int T;
const int maxn = 4000 + 5;
int A[maxn], B[maxn], C[maxn], D[maxn];
int sum[maxn*maxn];

int main(){
	cin >> T;
	while (T--){
		int n;
		cin >> n;
		for (int i = 0; i < n; i++){
			cin >> A[i] >> B[i] >> C[i] >> D[i];
		}
		int amount = 0;
		for (int i = 0; i < n; i++){
			for (int j = 0; j < n; j++){
				sum[amount++] = A[i] + B[j];
			}
		}
		sort(sum,sum+amount);
		int res = 0;
		for (int i = 0; i < n; i++){
			for (int j = 0; j < n; j++){
				res += upper_bound(sum, sum + amount, -C[i] - D[j]) -
					lower_bound(sum, sum + amount, -C[i] - D[j]);
			}
		}
		cout << res << endl;
		if (T) cout << endl;
 	}
}