feat : course-schedule

Author: ekgns33

course-schedule/ekgns33.java

@@ -0,0 +1,44 @@
+/*
+*
+* solution : topological sort
+* tc : O(E + V)
+* sc : O(E + V)
+*
+* */
+class Solution {
+  public boolean canFinish(int numCourses, int[][] prerequisites) {
+    List<Integer>[] adj = new ArrayList[numCourses];
+    for(int i = 0 ; i < numCourses; i++) {
+      adj[i] = new ArrayList<>();
+    }
+    boolean[] v = new boolean[numCourses];
+    int[] indeg = new int[numCourses];
+    for(int[] pre : prerequisites) {
+      int src = pre[0];
+      int dst = pre[1];
+      adj[src].add(dst);
+      indeg[dst]++;
+    }
+    Queue<Integer> q = new LinkedList<>();
+    for(int i = 0; i < numCourses; i ++) {
+      if(indeg[i] == 0) {
+        q.add(i);
+        v[i] = true;
+      }
+    }
+    int cnt= 0;
+    while(!q.isEmpty()) {
+      int curNode = q.poll();
+      cnt++;
+      for(int dst : adj[curNode]) {
+        indeg[dst]--;
+        if(indeg[dst] ==0 && !v[dst]) {
+          q.add(dst);
+        }
+      }
+    }
+
+    return cnt == numCourses;
+
+  }
+}