Create 207-Course-Schedule

java/207-Course-Schedule.java

@@ -0,0 +1,47 @@
+class Solution {
+    public boolean canFinish(int numCourses, int[][] prerequisites) {
+    Map<Integer, List<Integer>> adjList = new HashMap<Integer, List<Integer>>();
+    int[] indegree = new int[numCourses];
+
+      //creating the adjlist
+    for (int i = 0; i < prerequisites.length; i++) {
+      int post = prerequisites[i][0];
+      int pre = prerequisites[i][1];
+      List<Integer> lst = adjList.getOrDefault(pre, new ArrayList<Integer>());
+      lst.add(post);
+      adjList.put(pre, lst);
+
+      indegree[post] += 1;
+    }
+
+    Queue<Integer> q = new LinkedList<Integer>();
+    for (int i = 0; i < numCourses; i++) {
+      if (indegree[i] == 0) {
+        q.add(i);
+      }
+    }
+
+    int i = 0;
+    while (!q.isEmpty()) {
+      int node = q.remove();
+        i++;
+
+      if (adjList.containsKey(node)) {
+        for (Integer neighbor : adjList.get(node)) {
+          indegree[neighbor]--;
+
+          if (indegree[neighbor] == 0) {
+            q.add(neighbor);
+          }
+        }
+      }
+    }
+
+    if (i == numCourses) {
+      return true;
+    }
+
+    return false;
+  }
+
+}