poj1611

简单并查集

#include <iostream>
#include <cstdlib>
#include <cstdio>
#include <cstring>
using namespace std;

#define maxn 30005

int n, m;
int father[maxn];
int stk[maxn];

void init()
{
    for (int i = 0; i < n; i++)
        father[i] = i;
}

int getanc(int a)
{
    int top = 0;
    while (father[a] != a)
    {
        stk[top++] = a;
        a = father[a];
    }    
    while (top)
        father[stk[--top]] = a;
    return a;
}

void merge(int a, int b)
{
    int x = getanc(a);
    int y = getanc(b);
    father[x] = father[y];
}

void input()
{
    int k;
    for (int i = 0; i < m; i++)
    {
        scanf("%d", &k);
        if (k == 0)
            continue;
        int a, b;
        scanf("%d", &a);
        for (int j = 1; j < k; j++)
        {
            scanf("%d", &b);
            merge(a, b);
        }
    }
}

int work()
{
    int ret = 0;
    for (int i = 0; i < n; i++)
        if (getanc(i) == getanc(0))
            ret++;
    return ret;
}

int main()
{
    //freopen("t.txt", "r", stdin);
    while (scanf("%d%d", &n, &m), n | m)
    {
        init();
        input();
        printf("%d\n", work());
    }
    return 0;
}