小希的迷宫

#include<cstdio>
#include<set>
#include<iostream>
#include<cstring>
#include<algorithm>
using namespace std;
int p[100005];
int find(int x)
{
    return p[x]==x?x:p[x]=find(p[x]);
}
void solve()
{
    int u,v;
    while(1){
        set<int>s;
        int cnt=0,leap=0;
        for(int i=0;i<=100000;++i)
        p[i]=i;
    while(scanf("%d%d",&u,&v))
    {
        if(!u&&!v) break;
        if(u==-1&&v==-1) return;
        cnt++;
        if(u==v) continue;
        s.insert(u);s.insert(v);
        int x=find(u);int y=find(v);
        if(x==y) leap=1;
        else p[y]=x;
    }
    int cnt2=0;
    if(!cnt) {cout<<"Yes"<<endl;continue;}
    for(int i=1;i<=100000;++i) if(p[i]!=i) cnt2++;
    if(leap) cout<<"No"<<endl;
    else if(s.size()-cnt2>1) cout<<"No"<<endl;
    else cout<<"Yes"<<endl;
    }
}
int main()
{
   std::ios::sync_with_stdio(0);
    solve();
}

#include<cstdio>
#include<vector>
#include<queue>
#include<set>
#include<utility>
#include<iostream>
#include<cstring>
#include<algorithm>
#define MAXN 100000
using namespace std;
vector<int>G[MAXN];
set<int>s;
int vis[100000];
int g;
int ecnt;
void in_sert(int u,int v)
{
    s.insert(u);
    s.insert(v);
    G[u].push_back(v);
    G[v].push_back(u);
}
int readg()
{
    for(int i = 0 ;i < MAXN; i++)
    G[i].clear();
    s.clear();
    int u,v;
    cin>>u>>v;
    if(u==-1&&v==-1) return -1;
    if(!u&&!v) {cout<<"Yes"<<endl;return 0;}
    g=u;
    in_sert(u,v);
    ecnt=1;
    while(cin>>u>>v)
    {
        if(!u&&!v) break;
        ecnt++;
        in_sert(u,v);
    }
    return 1;
}
void bfs(int st)
{
    memset(vis,0,sizeof(vis));
    int now;
    queue<int>que;
    vis[st]=1;
    que.push(st);
    while(!que.empty())
    {
        now=que.front();
        que.pop();
        for(int i=0; i<G[now].size(); ++i)
        {
            if(!vis[G[now][i]])
            {
                que.push(G[now][i]);
                vis[G[now][i]]=1;
            }
        }
    }

}
int main()
{
    //freopen("case.txt","r",stdin);
    std::ios::sync_with_stdio(0);
    while(1){
    int t=readg();
    if(t==-1) break;
    if(!t) continue;
    bfs(G[g][0]);
    int cnt=0;
    for(int i=0; i<100000; ++i) if(!vis[i]) cnt++;
    if(MAXN-cnt==s.size()&&ecnt==s.size()-1) cout<<"Yes"<<endl;
    else cout<<"No"<<endl;
    }
}