说来惭愧啊。。现在才会并查集。我竟然给我妈妈讲明白并查集怎么回事了- -

#define  _CRT_SECURE_NO_WARNINGS

#include <iostream>

using namespace std;

#define maxx 50010

int set[maxx];

int find(int x)

{

	return x == set[x] ? x : (set[x] = find(set[x]));

}

int main()

{

	int n, m;

	int kase = 0;

	while (cin >> n >> m && (n || m))

	{

		for (int i = 1; i <= n; i++)

		{

			set[i] = i;

		}

		for (int i = 0; i < m; i++)

		{

			int a, b;

			scanf("%d %d", &a, &b);

			int c = find(a), d = find(b);

			if (c != d){ set[c] = d; }

		}

		int cnt = 0;

		for (int i = 1; i <= n; i++)

		{

			if (set[i] == i) cnt++;

		}

		cout << "Case " << ++kase << ": " << cnt << endl;

	}

}