POJ 1611 The Suspects

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题目大意：给你几个同学的集合，0为传染源，和他同组的都被传染，问有多少人被传染

最简单的并查集

结果忘了 if (rr1==rr2) return

RE了两次

#include<stdio.h>#include<stdlib.h>int parent[30001];int k;int findset(int x){ int tmp,s; s=x; while (parent[s]>=0) s=parent[s]; while (s!=x) {   tmp=parent[x];   parent[x]=s;   x=tmp; } return s;}void unionset(int r1,int r2){   int rr1,rr2;   rr1=findset(r1);   rr2=findset(r2);   int tmp=parent[rr1]+parent[rr2];   if (rr1==rr2) return;   if (parent[rr1]>parent[rr2]) {                  parent[rr1]=rr2;                  parent[rr2]=tmp;                 }             else {                    parent[rr2]=rr1;                    parent[rr1]=tmp;                  } return;}int main(){    int a,b,n,m; scanf("%d%d",&n,&m); while (n!=0 || m!=0) {   for (int i=0;i<=n;i++) parent[i]=-1;   for (int i=1;i<=m;i++)   {    scanf("%d%d",&k,&a);    for (int j=2;j<=k;j++)    {     scanf("%d",&b);     unionset(a,b);    }   }   printf("%d\n",-parent[findset(0)]);  scanf("%d%d",&n,&m);}}