POJ1611-The Suspects-并查集

#include <cstdio>
#include <algorithm>

using namespace std;

int n,m,k;

int fa[30010],sz[30010];

int Find(int x)
{
    while(x != fa[x])
    {
        fa[x] = fa[fa[x]];
        x = fa[x];
    }
    return x;
}

void Union(int p,int q)
{
    int fp = Find(p),fq = Find(q);
    if(fp == fq) return;
    if(sz[fp] < sz[fq])
    {
        fa[fp] = fq;
        sz[fq] += sz[fp];
    }
    else
    {
        fa[fq] = fp;
        sz[fp] += sz[fq];
    }
}

int main()
{
    while(scanf("%d%d",&n,&m) && (n||m))
    {
        for(int i=0;i<n;i++)
        {
            fa[i] = i;
            sz[i] = 1;
        }
        for(int i=0;i<m;i++)
        {
            scanf("%d",&k);
            int root = 0,p;
            for(int i=0;i<k;i++)
            {
                scanf("%d",&p);
                if(!i) root = p;
                else Union(p,root);
            }
        }
        printf("%d\n",sz[Find(0)]);
    }
}