1462. Course schedule IV

//1462. Course schedule IV

class Solution {
    public List<Boolean> checkIfPrerequisite(int numCourses, int[][] prerequisites, int[][] queries) {
        List<Integer>[] adj = new ArrayList[numCourses];
        boolean[][] prereq = new boolean[numCourses][numCourses];
        int[] inDegree = new int[numCourses];
        
        for(int i = 0; i < numCourses; i++) {
            adj[i] = new ArrayList<>();
        }
        
        for(int[] edge : prerequisites) {
            int a = edge[0], b = edge[1];
            adj[a].add(b);
            prereq[b][a] = true;
            inDegree[b]++;
        }
        
        Queue<Integer> q = new LinkedList<>();

        for(int i = 0; i < numCourses; i++) {
            if(inDegree[i] == 0) {
                q.add(i);
            }
        }
        
        while(!q.isEmpty()) {
            int u = q.poll();

            for(int v : adj[u]) {
                for(int i = 0; i < numCourses; i++) {
                    if(prereq[u][i]) {
                        prereq[v][i] = true;
                    }
                }

                if(--inDegree[v] == 0) {
                    q.add(v);
                }
            }
        }
        
        List<Boolean> ans = new ArrayList<>();

        for(int[] query : queries) {
            int u = query[0], v = query[1];
            ans.add(prereq[v][u]);
        }
        
        return ans;
    }
}