POJ - 1611（并查集）

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#include <iostream>
#include <cstdio>
#include <cstring>
#include <cmath>

using namespace std;

const int maxn = 30010;

int par[maxn];
int n, m;

int get_par(int a)
{
    if (par[a] != a) {
        par[a] = get_par (par[a]);//一定是a的父亲是a的父亲的根不要写错
    }
    return par[a];
}

int query(int a, int b)
{
    return get_par (a) == get_par (b);
}

void Merge(int a, int b)
{
    par[get_par(a)] = get_par(b);
}

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

int main()
{
    #ifndef ONLINE_JUDGE
    freopen ("in.txt", "r", stdin);
    #endif // ONLINE_JUDGE
    while (scanf ("%d%d", &n, &m) != EOF) {
        if (n == 0 && m == 0) break;
        Init ();
        for (int i = 0; i < m; i++) {
            int k, a;
            scanf ("%d%d", &k, &a);
            for (int j = 1; j < k; j++) {
                int b;
                scanf ("%d", &b);
                Merge (a, b);
            }
        }
        int num = 1;
        for (int i = 1; i < n; i++) {
            if (query (0, i)) {
                num++;
            }
        }
        printf ("%d\n", num);
    }
}