[HDOJ5365]Run

题目链接：http://acm.hdu.edu.cn/showproblem.php?pid=5365

众所周知，整点是围不成正三角形正五边形正六边形的，所以我们只需暴力出它可以围成几个正四边形。

#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <algorithm>
#include <iostream>
#include <cmath>
#include <cctype>
#include <queue>
#include <map>
#include <set>
#include <stack>
#include <list>
#include <vector>

using namespace std;

typedef struct Node {
    int x;
    int y;
};
Node po[22];
int edge[11];
int n;

int dis(int x, int y) {
    return x * x + y * y;
}
int solve() {
    memset(edge, 0, sizeof(edge));
    int ans = 0;
    for(int i = 0; i < n; i++) {
        for(int j = i+1; j < n; j++) {
            for(int p = j+1; p < n; p++) {
                for(int q = p+1; q < n; q++) {
                    edge[0] = dis(po[i].x-po[j].x, po[i].y-po[j].y);
                    edge[1] = dis(po[i].x-po[p].x, po[i].y-po[p].y);
                    edge[2] = dis(po[i].x-po[q].x, po[i].y-po[q].y);
                    edge[3] = dis(po[j].x-po[p].x, po[j].y-po[p].y);
                    edge[4] = dis(po[j].x-po[q].x, po[j].y-po[q].y);
                    edge[5] = dis(po[p].x-po[q].x, po[p].y-po[q].y);
                    sort(edge, edge+6);
                    if(edge[0] == edge[1] && edge[1] == edge[2] && edge[2] == edge[3] && edge[4] == edge[5]) {
                        ans++;
                    }
                }
            }
        }
    }
    return ans;
}
int main() {
    // freopen("in", "r", stdin);
    while(~scanf("%d", &n)) {
        for(int i = 0; i < n; i++) {
            scanf("%d %d", &po[i].x, &po[i].y);
        }
        printf("%d
", solve());
    }
}