UVa 1152 4 Values whose Sum is 0——二分

灵活使用STL

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>

using namespace std;
const int maxn = 4000 + 10;
int a[maxn], b[maxn], c[maxn], d[maxn], x[maxn*maxn];

int main()
{
    int T, n;
    cin >> T;
    while (T--) {
        cin >> n;
        for (int i = 0; i < n; i++) {
            cin >> a[i] >> b[i] >> c[i] >> d[i];
        }
        int cnt = 0;
        for (int i = 0; i < n; i++) {
            for (int j = 0; j < n; j++) {
                x[cnt++] = a[i] + b[j];
            }
        }
        sort(x, x + cnt);
        int ans = 0;
        for (int i = 0; i < n; i++) {
            for (int j = 0; j < n; j++) {
                ans += upper_bound(x, x + cnt, -c[i]-d[j]) - lower_bound(x, x + cnt, -c[i]-d[j]);
            }
        }
        printf("%d\n", ans);
        if (T) printf("\n");
    }
    return 0;
}