제출 #921661

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
921661		airmoon	Star triangles (IZhO11_triangle)	C++17	0 / 100	1 ms	600 KiB

triangle

#include <vector>
#include <algorithm>
#include <cstdio>
#include <string>
#include <utility>
#include <set>
#include <numeric>
#include <cmath>
#include <queue>
#include <stack>
#include <climits>
#include <map>
#include <iostream>

using namespace std;
using ll = long long;
using vi = vector<int>;
using vb = vector<bool>;
using vll = vector<ll>;
#define ff first
#define ss second
//#define int long long int

void setIO(string s) {
	freopen((s + ".in").c_str(), "r", stdin);
	freopen((s + ".out").c_str(), "w", stdout);
}

ll nCr(int n, int r){
	if(n<r) return 0;
	if(n==r) return 1;
	ll eto=1;
	for(int i=(n-2+1); i<=n; ++i){
		eto*=i;
	}
	return eto/4;
}

void solve(){
	int n; cin >> n;
	vector<pair<int,int>>a(n);
	map<int,int>cnt;
	int sum=0;
	for(int i=0; i<n; ++i){
		cin >> a[i].ff >> a[i].ss;
		cnt[a[i].ss]++;
	}
	for(auto &i : cnt){
		sum+=i.ss;
	}
	ll ans=0;
	for(int i=0; i<n; ++i){
		ans+=(nCr(sum-cnt[a[i].ss], 2));
	}
	cout << ans << "\n";
}

int main(){
//signed main(){
	//setIO("triangle");
	int T=1; 
	//cin >> T;
	for(int i=0; i<T; ++i) solve();
}

컴파일 시 표준 에러 (stderr) 메시지

triangle.cpp: In function 'void setIO(std::string)':
triangle.cpp:25:9: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   25 |  freopen((s + ".in").c_str(), "r", stdin);
      |  ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
triangle.cpp:26:9: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   26 |  freopen((s + ".out").c_str(), "w", stdout);
      |  ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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