POJ 1611 The Suspects（并查集）

题目链接

题目描述难懂。简单一句话，找和0在一个集合的。

#include <stdio.h>
#include <string.h>
int p[30001];
int find(int x)
{
    int t,r;
    r = x;
    while(x != p[x])
    {
        x = p[x];
    }
    while(r != x)
    {
        t = p[r];
        p[r] = x;
        r = t;
    }
    return x;
}
void merge(int x,int y)
{
    x = find(x);
    y = find(y);
    if(x != y)
    p[x] = y;
}
int main()
{
    int n,m,sv,ev,str,i,j,k,num;
    while(scanf("%d%d",&n,&m)!=EOF)
    {
        if(!n && !m) break;
        for(i = 0;i <= n-1;i ++)
        {
            p[i] = i;
        }
        for(i = 1;i <= m;i ++)
        {
            scanf("%d",&k);
            scanf("%d",&sv);
            for(j = 2;j <= k;j ++)
            {
                scanf("%d",&ev);
                merge(sv,ev);
            }
        }
        str = find(0);
        num = 0;
        for(i = 0;i <= n-1;i ++)
        {
            if(str == find(i))
            num ++;
        }
        printf("%d\n",num);
    }
    return 0;
}