Merge pull request neetcode-gh#165 from r1cky0/patch-11

Create 207-Course-Schedule.java

Author: neetcode-gh

java/207-Course-Schedule.java

@@ -0,0 +1,39 @@
+class Solution {
+    public boolean canFinish(int numCourses, int[][] prerequisites) {
+        List<List<Integer>> adj = new ArrayList<>();
+        for (int i = 0; i < numCourses; i++) {
+            adj.add(new ArrayList<>());
+        }
+        
+        for (int i = 0; i < prerequisites.length; i++) {
+            adj.get(prerequisites[i][0]).add(prerequisites[i][1]);
+        }
+        
+        int[] visited = new int[numCourses];
+        for (int i = 0; i < numCourses; i++) {
+            if (visited[i] == 0) {
+                if (isCyclic(adj, visited, i)) {
+                    return false;
+                }
+            }
+        }
+        return true;
+    }
+    
+    private boolean isCyclic(List<List<Integer>> adj, int[] visited, int curr) {
+        if (visited[curr] == 2) {
+            return true;
+        }
+        
+        visited[curr] = 2;
+        for (int i = 0; i < adj.get(curr).size(); i++) {
+            if (visited[adj.get(curr).get(i)] != 1) {
+                if (isCyclic(adj, visited, adj.get(curr).get(i))) {
+                    return true;
+                }
+            }
+        }
+        visited[curr] = 1;
+        return false;
+    }
+}