import java.util.*;

/**

* Author : WindAsMe

* File : findOrder.java

* Time : Create on 18-9-4

* Location : ../Home/JavaForLeeCode2/findOrder.java

* Function : LeetCode No.210

*/

public class findOrder {

private static int[] findOrderResult(int numCourses, int[][] prerequisites) {

int[] map = new int[numCourses];

int[] res = new int[numCourses];

for (int[] prerequisite : prerequisites)

map[prerequisite[1]]++;

Queue<Integer> que = new LinkedList<>();

int index = numCourses - 1;

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

if(map[i] == 0) {

que.add(i);

res[index--] = i;

}

}

while(!que.isEmpty() ){

int k = que.remove();

for (int[] prerequisite : prerequisites) {

int l = prerequisite[1];

if (k == prerequisite[0]) {

map[l]--;

if (map[l] == 0) {

que.add(l);

res[index--] = l;

}

}

}

}

if(index != -1)

return new int[0];

else

return res;

}

public static void main(String[] args) {

int[][] pre = {

{1,0}

// {2,0},

// {3,1},

// {3,2}

};

System.out.println(Arrays.toString(findOrderResult(5, pre)));

}

}