package LeetCode;

import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.Deque;



public class LC_207 {
    static ArrayList<ArrayList<Integer>> list = new ArrayList<>();
    static Deque<Integer> que = new ArrayDeque<Integer>();
    public static void main(String[] args ) {
        System.out.println(canFinish(3, new int[][]{{1,0},{0,2}}));
    }
    public static boolean canFinish(int numCourses, int[][] prerequisites) {
        int[] indeg = new int[numCourses];
        for (int i = 0; i < numCourses; i++) {
            list.add(new ArrayList<Integer>());
        }
        for (int i = 0; i < prerequisites.length; i++) {
            list.get(prerequisites[i][1]).add(prerequisites[i][0]);
            indeg[prerequisites[i][0]]++;
        }
        for (int i = 0; i < indeg.length; i++) {
            if (indeg[i] == 0)
                que.add(i);
        }
        int count = 0;
        while (!que.isEmpty()) {
            count++;
            int u = que.poll();
            for (int v : list.get(u)) {
                indeg[v]--;
                if (indeg[v] == 0)
                    que.add(v);
            }

        }
        return count == numCourses;
    }
}