ACM HDOJ 1272 (小希的迷宮)

題目鏈接 http://acm.hdu.edu.cn/showproblem.php?pid=1272

import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner scn = new Scanner(System.in);
		DisjointSet disjointSet = new DisjointSet();
		int count = 0;
		boolean tree = true;
		while (true) {
			int number1 = Integer.parseInt(scn.next());
			int number2 = Integer.parseInt(scn.next());
			if (-1 == number1 && -1 == number2) {
				break;
			}
			if (0 == number1 && 0 == number2) {
				if (tree) {
					for (int i = 0; i < disjointSet.getSIZE(); ++i) {
						if (disjointSet.getRecordItem(i)
								&& disjointSet.getFlagItem(i) == i) {
							++count;
							if (count > 1) {
								break;
							}
						}
					}
					if (1 < count) {
						System.out.println("No");
					} else {
						System.out.println("Yes");
					}
				} else {
					System.out.println("No");
				}
				disjointSet = new DisjointSet();
				count = 0;
				tree = true;
				continue;
			}
			if (tree) {
				tree = disjointSet.union(number1 - 1, number2 - 1);
			}
		}
		scn.close();
	}

}

class DisjointSet {

	private final int SIZE = 100001;
	private int[] flag;
	private boolean[] record;

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

	public DisjointSet() {
		flag = new int[SIZE];
		for (int i = 0; i < SIZE; ++i) {
			flag[i] = i;
		}
		record = new boolean[SIZE];
	}

	public boolean union(int x, int y) {
		record[x] = true;
		record[y] = true;
		boolean tree = true;
		int xRoot = find(x);
		int yRoot = find(y);
		if (xRoot == yRoot) {
			tree = false;
		}
		if (xRoot != yRoot) {
			flag[yRoot] = xRoot;
		}
		return tree;
	}

	public int getSIZE() {
		return SIZE;
	}

	public int getFlagItem(int i) {
		return flag[i];
	}

	public boolean getRecordItem(int i) {
		return record[i];
	}

}