简单几何(水）BestCoder Round #50 (div.2) 1002 Run

题目传送门

 /*
     好吧，我不是地球人，这题只要判断正方形就行了，正三角形和正五边形和正六边形都不可能(点是整数)。
     但是，如果不是整数，那么该怎么做呢？是否就此开启计算几何专题了呢
 */
 /************************************************
  * Author        :Running_Time
  * Created Time  :2015-8-8 19:54:14
  * File Name     :B.cpp
  ************************************************/

 #include <cstdio>
 #include <algorithm>
 #include <iostream>
 #include <sstream>
 #include <cstring>
 #include <cmath>
 #include <string>
 #include <vector>
 #include <queue>
 #include <deque>
 #include <stack>
 #include <list>
 #include <map>
 #include <set>
 #include <bitset>
 #include <cstdlib>
 #include <ctime>
 using namespace std;

 #define lson l, mid, rt << 1
 #define rson mid + 1, r, rt << 1 | 1
 typedef long long ll;
 const int MAXN = ;
 const int INF = 0x3f3f3f3f;
 const int MOD = 1e9 + ;
 struct Point    {
     int x, y;
 }p[MAXN];
 int id[];
 int n, tot;

 int cal_dis(int x1, int y1, int x2, int y2)    {
     return (x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2);
 }

 bool judge(void) {
     int tt = ; int d[];
     for (int i=; i<=; ++i)    {
         for (int j=i+; j<=; ++j)  {
             d[++tt] = cal_dis (p[id[i]].x, p[id[i]].y, p[id[j]].x, p[id[j]].y);
         }
     }
     sort (d+, d++tt);
     for (int i=; i<=; ++i)    if (d[i] != d[i+]) return false;
     if (d[] != d[])   return false;
     if (d[] != d[] * )   return false;
     return true;
 }

 void DFS(int s, int num)    {
     if (num == )   {
         if (judge ())    tot++;
         return ;
     }
     for (int i=s+; i<=n; ++i)  {
         id[num+] = i;
         DFS (i, num + );
     }
 }

 void work(void) {
     tot = ;
     DFS (, );
     printf ("%d\n", tot);
 }

 int main(void)    {     //BestCoder Round #50 (div.2) 1002 Run
     while (scanf ("%d", &n) == )   {
         for (int i=; i<=n; ++i)    {
             scanf ("%d%d", &p[i].x, &p[i].y);
         }
         if (n < )  {
             puts (""); continue;
         }
         work ();
     }

     return ;
 }