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  1. #include <iostream>
  2.  
  3. const int N = 2005;
  4.  
  5. int x[N], y[N];
  6. int n;
  7.  
  8. int main() {
  9.   std::ios_base::sync_with_stdio(0);
  10.   std::cin.tie(0);
  11.   std::cin >> n;
  12.   for (int i = 1; i <= n; i++) {
  13.     std::cin >> x[i] >> y[i];
  14.   }
  15.   int ans = 0;
  16.   for (int i = 3; i <= n; i++) {
  17.     double a[N];
  18.     for (int j = 1; j < i; j++) {
  19.       if (x[i] == x[j]) {
  20.         a[j] = -1e9;
  21.       } else {
  22.         a[j] = 1. * (y[i] - y[j]) / (x[i] - x[j]);
  23.       }
  24.     }
  25.     for (int j = 1; j < i; j++) {
  26.       for (int k = j + 1; k < i; k++) {
  27.         ans += a[j] == a[k];
  28.       }
  29.     }
  30.   }
  31.   std::cout << ans;
  32.   return 0;
  33. }
  34.  
Success #stdin #stdout 0.01s 5280KB
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https://ideone.com/wqMOQE
language:
C++14 (gcc 8.3)
created:
21 days ago
visibility:
public

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