题目1109：连通图

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#include <iostream>#include <stdio.h>#include <algorithm>#include <math.h>#include <string>#include <string.h>#include <vector>#include <queue>#include <stack>using namespace std;//1109 method2int T[1010];void init(int n){    for(int i=1;i<=n;i++){        T[i]=i;    }}//查找根并进行路径优化int findRoot(int x){    if(T[x]==x) return x;    else{        int t=findRoot(T[x]);        T[x]=t;        return t;    }}void unio(int a,int b){    if(a!=b)        T[a]=b;}int main(){    int n,m;    //freopen("E://PAT/input.txt","r",stdin);    while(scanf("%d %d",&n,&m)!=EOF&&n!=0){        init(n);        while(m--){            int a,b;scanf("%d %d",&a,&b);            a=findRoot(a),b=findRoot(b);            unio(a,b);        }        int cnt=0;        for(int i=1;i<=n;i++)            if(T[i]==i) cnt++;        printf("%s\n",cnt>1?"NO":"YES");    }}/**************************************************************    Problem: 1109    User: cust123    Language: C++    Result: Accepted    Time:20 ms    Memory:1524 kb****************************************************************/
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