Solution2.java

class Solution {
    public List<Boolean> checkIfPrerequisite(int n, int[][] prerequisites, int[][] queries) {
        boolean[][] f = new boolean[n][n];
        List<Integer>[] g = new List[n];
        int[] indeg = new int[n];
        Arrays.setAll(g, i -> new ArrayList<>());
        for (var p : prerequisites) {
            g[p[0]].add(p[1]);
            ++indeg[p[1]];
        }
        Deque<Integer> q = new ArrayDeque<>();
        for (int i = 0; i < n; ++i) {
            if (indeg[i] == 0) {
                q.offer(i);
            }
        }
        while (!q.isEmpty()) {
            int i = q.poll();
            for (int j : g[i]) {
                f[i][j] = true;
                for (int h = 0; h < n; ++h) {
                    f[h][j] |= f[h][i];
                }
                if (--indeg[j] == 0) {
                    q.offer(j);
                }
            }
        }
        List<Boolean> ans = new ArrayList<>();
        for (var qry : queries) {
            ans.add(f[qry[0]][qry[1]]);
        }
        return ans;
    }
}