UVa problem 10305(Ordering Tasks)

You can read problem description here.

Topological Sort algorithm is used to solve this problem.

	import java.util.ArrayList;
	import java.util.Scanner;

	public class Main {
	static boolean[] visited;
	static int[] res;
	static int index;
	static ArrayList<Integer>[] adj;

	private static void toposort() {
	for (int i = 0; i < adj.length; i++) {
	explore(i);
	}
	}

	private static void explore(int s) {
	if (!visited[s]) {
	visited[s] = true;
	for (int i = 0; i < adj[s].size(); i++) {
	explore(adj[s].get(i));
	}
	res[index++] = s;
	}
	}

	public static void main(String[] args) {
	Scanner scanner = new Scanner(System.in);
	int n = scanner.nextInt();
	int m = scanner.nextInt();
	while (true) {
	adj = (ArrayList<Integer>[]) new ArrayList[n];
	for (int i = 0; i < n; i++) {
	adj[i] = new ArrayList<Integer>();
	}
	for (int i = 0; i < m; i++) {
	int x, y;
	x = scanner.nextInt();
	y = scanner.nextInt();
	adj[y - 1].add(x - 1);
	}
	visited = new boolean[n];
	res = new int[n];
	index = 0;
	toposort();
	for (int i = 0; i < res.length - 1; i++) {
	System.out.print(res[i] + 1 + " ");
	}
	System.out.println(res[n - 1] + 1);
	n = scanner.nextInt();
	m = scanner.nextInt();
	if (n == 0)
	break;
	}
	scanner.close();
	}
	}

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