poj 1611 初级并查集

看并查集算法也有一段时间了，苦于没时间练手，呵呵！昨天把CCNA考试考完了，做了第一道初级并查集的题，有了较深刻的理解，发出来共享下，大家一起学习学习。

http://acm.pku.edu.cn/JudgeOnline/problem?id=1611

这道题主要的意思是：找和0一组的人有关系的人总数。

import java.util.Arrays;
import java.util.Scanner;

public class Main {
	static int[] student;
	static int[] ans;

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		while (sc.hasNext()) {
			int n = sc.nextInt();
			int m = sc.nextInt();

			if (n == 0 && m == 0)
				break;
			student = new int[n];

			ans = new int[n];
			Arrays.fill(ans, 1);
			for (int i = 0; i < n; ++i) {
				student[i] = i;
			}
			for (int i = 0; i < m; ++i) {
				int k = sc.nextInt();
				int x = sc.nextInt();
				for (int j = 0; j < k - 1; ++j) {
					int y = sc.nextInt();
					unin(x, y);
					// student[y] = x;
					// x = y;
				}
			}
			System.out.println(ans[find(0)]);
			// for (int i = 0; i < n; ++i)
			// System.out.println(i + ":" + student[i]);
		}
	}

	static void unin(int x, int y) {

		int px = find(x);
		int py = find(y);
		if (px == py)
			return;
		else {
			// System.out.println("py=" + py + ";px=" + px);
			if (px > py) {
				student[py] = px;
				ans[px] = ans[px] + ans[py];
				// System.out.println("ans["+px+"]="+ans[px]);
			} else {
				student[px] = py;
				ans[py] = ans[px] + ans[py];
				// System.out.println("ans["+py+"]="+ans[py]);
			}
		}
	}

	static int find(int x) {
		// ans++;
		int p = student[x];
		// System.out.println("p=" + p);
		if (p == x)
			return p;
		else
			return find(p);
	}
}