제출 #1255250

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
1255250		bonic	별들과 삼각형 (IZhO11_triangle)	C++20	0 / 100	2 ms	320 KiB

triangle

#include <bits/stdc++.h>
using namespace std;
#define int long long

signed main() {
    freopen("triangles.in","r",stdin);
    int n; cin >> n; vector<int> X(n); vector<int> Y(n);
    vector<pair<int, int>> A(n);
    for (int i = 0; i < n; i++) {
        int x, y; cin >> x >> y;
        A[i] = {x, y};
        X[i] = x; Y[i] = y;
    }
    sort(X.begin(), X.end()); sort(Y.begin(), Y.end()); int sum = 0;
    for (int i = 0; i < n; i++) {
        int q = A[i].first; int w = A[i].second;
        int a = (upper_bound(X.begin(), X.end(), q) - X.begin()) - (lower_bound(X.begin(), X.end(), q) - X.begin());
        int b = (upper_bound(Y.begin(), Y.end(), w) - Y.begin()) - (lower_bound(Y.begin(), Y.end(), w) - Y.begin());
        // cout << a-1 << " " << b-1 << "\n";
        sum += (a-1) * (b-1);
    }
    freopen("triangles.out","w",stdout);
    cout << sum;
}

컴파일 시 표준 에러 (stderr) 메시지

triangle.cpp: In function 'int main()':
triangle.cpp:6:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
    6 |     freopen("triangles.in","r",stdin);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~
triangle.cpp:22:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   22 |     freopen("triangles.out","w",stdout);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~

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