ACM HDOJ 1213 (How Many Tables )

題目鏈接 http://acm.hdu.edu.cn/showproblem.php?pid=1213

import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner scn = new Scanner(System.in);
		int casesNumber = Integer.parseInt(scn.next());
		while (0 <= --casesNumber) {
			int pointsNumber = Integer.parseInt(scn.next());
			DisjointSet disjointSet = new DisjointSet(pointsNumber);
			int relationNumber = Integer.parseInt(scn.next());
			while (0 <= --relationNumber) {
				int x = Integer.parseInt(scn.next()) - 1;
				int y = Integer.parseInt(scn.next()) - 1;
				disjointSet.union(x, y);
			}
			System.out.println(disjointSet.calculateSetNumber());
		}
		scn.close();
	}

}

class DisjointSet {

	private int pointsNumber;
	private int[] flag;

	private int find(int r) {
		while (r != flag[r]) {
			r = flag[r];
		}
		return r;
	}

	public DisjointSet(int pointsNumber) {
		this.pointsNumber = pointsNumber;
		flag = new int[pointsNumber];
		for (int i = 0; i < pointsNumber; ++i) {
			flag[i] = i;
		}
	}

	public int calculateSetNumber() {
		int count = 0;
		for (int i = 0; i < pointsNumber; ++i) {
			if (flag[i] == i) {
				++count;
			}
		}
		return count;
	}

	public void union(int x, int y) {
		int xRoot = find(x);
		int yRoot = find(y);
		if (xRoot != yRoot) {
			flag[yRoot] = xRoot;
		}
	}

}