欢乐PC杯 Round 2 官方代码

#include<iostream>
#include<set>
#include<map>
#define int long long
using namespace std;
map<int,set<int>> mp;
int n,p,x,y,p1,p2;
signed main(){
	cin>>n;
	for(int i=1;i<=n;++i){
		cin>>x>>y;
		mp[x].insert(y);
		mp[y].insert(x);
	}
	cin>>p;
	while(p--){
		cin>>p1>>p2;
		if(mp[p1].count(p2)) cout<<"yes"<<endl;
		else cout<<"no"<<endl;
	}
    return 0;
}

#include<iostream>
#include<cstring>
#include<vector>
#include<queue>
using namespace std;
const int maxn=1e3+10;
int n,m,cnt;
vector<int> G[maxn];
bool vis[maxn];
void dfs(int u){
	vis[u]=true;
	for(auto v:G[u]){
		if(vis[v]) continue;
		dfs(v);
	}
}
int main(){
	cin>>n>>m;
	for(int i=1;i<=m;++i){
		int u,v;
		cin>>u>>v;
		G[u].push_back(v);
		G[v].push_back(u);
	}
	for(int i=2;i<=n-1;++i){
		memset(vis,false,sizeof(vis));
		vis[i]=true;
		dfs(1);
		if(!vis[n]) cnt++;
	}
	cout<<cnt;
	return 0;
}