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  1.  
  2. #include <bits/stdc++.h>
  3.  
  4. using namespace std;
  5.  
  6. #define int long long
  7. #define nn "\n"
  8. #define pi pair<int, int>
  9. #define fi first
  10. #define se second
  11. #define lb lower_bound
  12. #define ub upper_bound
  13. #define eb emplace_back
  14. #define pb push_back
  15. #define TASK "CTAMGIACV"
  16.  
  17. #define ms(a, x) memset(a, x, sizeof(a))
  18. #define all(a) a.begin(), a.end()
  19. #define All(a, n) a + 1, a + 1 + n
  20.  
  21. #define LOG 19
  22.  
  23. const int INF = 1e18;
  24. const int mod = 1e9;
  25. const int N = 1e5 + 5;
  26. const int MOD = 998244353;
  27. int n;
  28. pi p[505];
  29.  
  30. void nhap(){
  31.     cin >> n;
  32.     for(int i = 1; i <= n; i++){
  33.         cin >> p[i].fi >> p[i].se;
  34.     }
  35. }
  36.  
  37. void solve(){
  38.     int ans = 0;
  39.     for(int i = 1; i <= n; i++){
  40.         for(int j = i + 1; j <= n; j++){
  41.             for(int k = j + 1; k <= n; k++){
  42.                 int x1 = p[j].fi - p[i].fi;
  43.                 int y1 = p[j].se - p[i].se;
  44.                 int x2 = p[k].fi - p[i].fi;
  45.                 int y2 = p[k].se - p[i].se;
  46.                 if(x1 * x2 + y1 * y2 == 0){
  47.                     ans++;
  48.                     continue;
  49.                 }
  50.                 x1 = p[i].fi - p[j].fi;
  51.                 y1 = p[i].se - p[j].se;
  52.                 x2 = p[k].fi - p[j].fi;
  53.                 y2 = p[k].se - p[j].se;
  54.                 if(x1 * x2 + y1 * y2 == 0){
  55.                     ans++;
  56.                     continue;
  57.                 }
  58.                 x1 = p[i].fi - p[k].fi;
  59.                 y1 = p[i].se - p[k].se;
  60.                 x2 = p[j].fi - p[k].fi;
  61.                 y2 = p[j].se - p[k].se;
  62.                 if(x1 * x2 + y1 * y2 == 0){
  63.                     ans++;
  64.                 }
  65.             }
  66.         }
  67.     }
  68.     cout << ans << nn;
  69. }
  70. signed main(){
  71.     if(fopen(TASK".INP", "r")){
  72.         freopen(TASK".INP", "r", stdin);
  73.         freopen(TASK".OUT", "w", stdout);
  74.     }
  75.     ios_base::sync_with_stdio(0);
  76.     cin.tie(0);
  77.     cout.tie(0);
  78.     nhap();
  79.     solve();
  80.     return (0 ^ 0);
  81. }
  82.  
Success #stdin #stdout 0s 5312KB
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https://ideone.com/0RNPUA
language:
C++14 (gcc 8.3)
created:
4 hours ago
visibility:
public

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