hdu1272 小希的迷宫 并查集

#include<iostream>#include<cstdio>#include<cmath>#include<algorithm>#include<memory.h>#include<map>#include<queue>#include <deque>#include <list>#include <ctime>#include <stack>#include <vector>#include<set>#define Maxn 100005typedef long long ll;#define rep(i,j,n) for(int i=j;i<=n;i++)#define per(i,j,k) for(int i=j;i>=k;--i)#define lowbit(a) a&-a#define Max(a,b) a>b?a:b#define Min(a,b) a>b?b:aconst int inf = 0x3f3f3f3f;const double pi = acos(-1.0);using namespace std;int father[Maxn],flag,sign[Maxn];void init(){   for(int i=1;i<Maxn;i++)    {father[i]=i;    sign[i]=0;    }}int getf(int x){   if(x!=father[x])    father[x]=getf(father[x]);    return father[x];}void Union(int x,int y){   x=getf(x);    y=getf(y);    if(x!=y)    father[x]=y;    else flag=0;//判断是否成环}int main(){   int a,b;    while(~scanf("%d%d",&a,&b))    {   if(a==-1&&b==-1) break;        if(a==0 && b==0){printf("Yes\n");continue;}        init();        sign[a]=sign[b]=1;        flag=1;        Union(a,b);        while(~scanf("%d%d",&a,&b)&&a&&b)        {        Union(a,b);        sign[a]=sign[b]=1;        }        int k=0,ans=0;        for(int i=1;i<Maxn;i++)        {            if( sign[i]&& father[i]==i) //判断根节点k数目                k++;            if(k>1) flag=0;        }        if(flag) printf("Yes\n");        else  printf("No\n");    }    return 0;}