判定简单图代码

#include <bits/stdc++.h>
using namespace std;
int d[1001][1001];
int main() {
	int n, m;
	cin >> n >> m;
	bool f = true;
	for (int i = 1; i <= m; i++) {
		int a, b;
		cin >> a >> b;
		if (a == b) {
			f = false;
			break;
		}
		if(d[a][b]){
			f=false;
			break;
		}
		d[a][b]=1;
		d[b][a]=1;
	}
	if(f){
		cout << "Yes";
	}else{
		cout << "No";
	}
	return 0;
}