Tunnels

import java.util.*;

/**
 * Created by Florian on 22-Jan-17.
 */
public class Tunnels2 {
	public static void main(String args[]) {
		Scanner sc = new Scanner(System.in);
		StringTokenizer st = new StringTokenizer(sc.nextLine());
		int n = Integer.parseInt(st.nextToken());
		int m = Integer.parseInt(st.nextToken());
		int[] incoming = new int[n];//
		ArrayList<Queue<Integer>> connections = new ArrayList<>();
		for (int i = 0; i < n; i++) {
			connections.add(new LinkedList<>());
		}

		for (int i = 0; i < m; i++) {
			st = new StringTokenizer(sc.nextLine());
			int a = Integer.parseInt(st.nextToken()) - 1;
			int b = Integer.parseInt(st.nextToken()) - 1;
//			inoutDif[a]++;
//			inoutDif[b]--;
			incoming[b]++;
			connections.get(a).add(b);
//			connections.get(b).add(a);
		}
		int[] ordered = new int[n];
		LinkedList<Integer> noIn = new LinkedList<>();
		for (int i = 0; i < n; i++) {
			if (incoming[i] == 0)
				noIn.add(i);
		}
		int count = 0;
		int node;
		while (!noIn.isEmpty()) {
			node = noIn.poll();
			ordered[count++] = node;
			for (Integer next : connections.get(node)) {
				incoming[next]--;
				if (incoming[next] == 0)
					noIn.add(next);
			}
		}

		int[] arriving = new int[n];
		int dUsed = 0;
		for (int i = 0; i < n; i++) {
			node = ordered[i];
			dUsed += Math.max(0, connections.get(node).size() - arriving[node]);
			for (Integer next : connections.get(node)) {
				arriving[next]++;
			}
		}
		System.out.println(dUsed);

	}

}

Test 1

Group: 1

Verdict: ACCEPTED

Test 2

Group: 1

Verdict: ACCEPTED

Test 3

Group: 1

Verdict: ACCEPTED

Test 4

Group: 1

Verdict: ACCEPTED

Test 5

Group: 1

Verdict: ACCEPTED

Test 6

Group: 2

Verdict: ACCEPTED

Test 7

Group: 2

Verdict: ACCEPTED

Test 8

Group: 2

Verdict: ACCEPTED

Test 9

Group: 2

Verdict: ACCEPTED

Test 10

Group: 2

Verdict: ACCEPTED

Test 11

Group: 3

Verdict: TIME LIMIT EXCEEDED

Test 12

Group: 3

Verdict: ACCEPTED

Test 13

Group: 3

Verdict: ACCEPTED

Test 14

Group: 3

Verdict: ACCEPTED

Test 15

Group: 3

Verdict: ACCEPTED