public class Solution {

private int N = 0;

public int[] findOrder(int numCourses, int[][] prerequisites) {

int[] result = new int[numCourses];

Course[] courses = new Course[numCourses];

for (int i = 0; i < numCourses; i++) {

courses[i] = new Course(i);

}

for (int i = 0; i < prerequisites.length; i++) {

courses[prerequisites[i][0]].add(courses[prerequisites[i][1]]);

}

for (int i = 0; i < numCourses; i++) {

if (isCyclic(courses[i], result)) {

return new int[0];

}

}

return result;

}

private boolean isCyclic(Course cur, int[] result) {

if (cur.tested == true) return false;

if (cur.visited == true) return true;

cur.visited = true;

for (Course c : cur.pre) {

if (isCyclic(c, result)) {

return true;

}

}

cur.tested = true;

result[N++] = cur.number;

return false;

}

class Course {

boolean visited = false;

boolean tested = false;

int number;

List<Course> pre = new ArrayList<Course>();

public Course(int i) {

number = i;

}

public void add(Course c) {

pre.add(c);

}

}

}