poj2524

简单并查集

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

#define maxn 50004

int father[maxn];

int getanc(int a)
{
    if (father[a] == a)
        return a;
    return father[a] = getanc(father[a]);
}

void merge(int a, int b)
{
    if (father[a] == -1)
        father[a] = a;
    if (father[b] == -1)
        father[b] = b;
    father[getanc(a)] = getanc(b);
}

int main()
{
//    freopen("t.txt", "r", stdin);
    int t = 0;
    int n, m;
    while (scanf("%d%d", &n, &m), n | m)
    {
        memset(father, -1, sizeof(father));
        t++;
        for (int i = 0; i < m; i++)
        {
            int a, b;
            scanf("%d%d", &a, &b);
            a--;
            b--;
            merge(a, b);
        }
        int ans = 0;
        for (int i = 0; i < n; i++)
            if (father[i] == -1 || father[i] == i)
                ans++;
        printf("Case %d: %d\n", t, ans);
    }
    return 0;
}