1class Solution {2    public boolean canFinish(int numCourses, int[][] prerequisites) {3        List<List<Integer>> graph = new ArrayList<>();4        for (int i = 0; i < numCourses; i++) graph.add(new ArrayList<>());5        int[] indegree = new int[numCourses];6        for (int[] edge : prerequisites) {7            graph.get(edge[1]).add(edge[0]);8            indegree[edge[0]]++;9        }10        Deque<Integer> queue = new ArrayDeque<>();11        for (int i = 0; i < numCourses; i++) if (indegree[i] == 0) queue.add(i);12        int completed = 0;13        while (!queue.isEmpty()) {14            int course = queue.remove(); completed++;15            for (int next : graph.get(course)) {16                if (--indegree[next] == 0) queue.add(next);17            }18        }19        return completed == numCourses;20    }21}