【简单几何】CF Edu11 D

拼搏现实的明天。 2024-03-08 08:21 96阅读 0赞

[Problem - D - Codeforces][]

题意：

![dc204ef2a0e44465bfc3ca02f80670ee.png][]

思路：

和蓝桥杯国赛有道题类似，都是用中点来确定图形防止精度缺失

应该算是典

![a3d0238b4449449bb532a133ee8913e8.png][]

Code：

#include <bits/stdc++.h>
    
    using i64 = long long;
    
    constexpr int N = 2e3 + 10;
    constexpr int M = 1e6 + 10;
    constexpr int P = 2600;
    constexpr i64 Inf = 1e18;
    constexpr int mod = 1e9 + 7;
    constexpr double eps = 1e-6;
    
    
    int n;
    int x[N], y[N];
    
    void solve() {
        std::cin >> n;
        for (int i = 1; i <= n; i ++) std::cin >> x[i] >> y[i];
    
        std::map<std::pair<int,int> ,int> mp;
        for (int i = 1; i <= n; i ++) {
            for (int j = i + 1; j <= n; j ++) {
                int a = x[i] + x[j];
                int b = y[i] + y[j];
                mp[{a, b}] ++;
            }
        }
    
        int ans = 0;
        for (auto t : mp) {
            int cnt = t.second;
            int k = cnt * (cnt - 1) / 2;
            ans += k;
        }
    
        std::cout << ans << "\n";
    }
    signed main() {
        std::ios::sync_with_stdio(false);
        std::cin.tie(nullptr);
        
        int t = 1;
    
        while (t--) {
            solve();
        }
        
        return 0;
    }

[Problem - D - Codeforces]: https://codeforces.com/contest/660/problem/D
[dc204ef2a0e44465bfc3ca02f80670ee.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/08/c017113318ac468a8220f1605d045023.png
[a3d0238b4449449bb532a133ee8913e8.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/08/db3b8b792d51495e925fc3f53dd72175.png