数学 Codeforces Round #291 (Div. 2) B. Han Solo and Lazer Gun

  1 /*
  2     水题，就是用三点共线的式子来判断射击次数
  3 */
  4 #include <cstdio>
  5 #include <cmath>
  6 #include <string>
  7 #include <cstring>
  8 #include <iostream>
  9 #include <algorithm>
 10 #include <map>
 11 #include <set>
 12 #include <vector>
 13 using namespace std;
 14 
 15 const int MAXN = 1e3 + 10;
 16 int x[MAXN], y[MAXN];
 17 bool used[MAXN];
 18 
 19 int main(void)
 20 {
 21     //freopen ("B.in", "r", stdin);
 22     
 23     int n, x0, y0;
 24     
 25     while (~scanf ("%d%d%d", &n, &x0, &y0))
 26     {
 27         memset (used, 0, sizeof (used));
 28         
 29         for (int i=1; i<=n; ++i)
 30         {
 31             scanf ("%d%d", &x[i], &y[i]);
 32             x[i] -= x0;  y[i] -= y0;
 33         }
 34         
 35         int cnt = 0;
 36         for (int i=1; i<=n; ++i)
 37         {
 38             if (!used[i])
 39             {
 40                 cnt++;
 41                 for (int j=i; j<=n; ++j)
 42                 {
 43                     if (!used[j] && (x[i] * y[j] == x[j] * y[i]))
 44                         used[j] = 1;
 45                 }
 46             }
 47         }
 48         
 49         printf ("%d
", cnt);
 50     }
 51     
 52     return 0;
 53 }
编译人生，运行世界！