hdu1272小希的迷宫

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//代码含全角空格

#include <iostream>#include <cstdio>#include <cstring>using namespace std;const int N=100005;//考虑同一连通图中有圈(不为树),图不连通(森林)int root=0,n,m,fa[N],vis[N];void inti(){    for(int i=1;i<=N;i++){        fa[i]=i;    }}int find(int x){    while(x!=fa[x]) x=fa[x]=fa[fa[x]]; return x;}void merge(int x,int y){        if(find(x)==find(y)){            root=2;            return ;        }        fa[find(y)]=find(x);}int main(){    inti();    int maxn=0;    while(scanf("%d%d",&n,&m)==2&&n!=-1&&m!=-1){        if(!n||!m){            for(int i=1;i<=maxn;i++){                if(fa[i]==i&&vis[i])root++;            }            if(maxn==1||!maxn){cout<<"Yes"<<endl;continue;}            if(root!=1)cout<<"No"<<endl;            else cout<<"Yes"<<endl;            inti();            root=maxn=0;            memset(vis,0,sizeof(vis));        }        else{            maxn=max(maxn,n);            maxn=max(maxn,m);            vis[n]=vis[m]=1;            merge(n,m);        }    }    return 0;}

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