Create Course Schedule II - Leetcode 210.py

Author: gahogg

Course Schedule II - Leetcode 210.py

@@ -0,0 +1,33 @@
+class Solution:
+    def findOrder(self, numCourses: int, prerequisites: List[List[int]]) -> List[int]:
+        order = []
+        g = defaultdict(list)
+        for a, b in prerequisites:
+            g[a].append(b)
+        
+        UNVISITED, VISITING, VISITED = 0, 1, 2
+        states = [UNVISITED] * numCourses
+
+        
+        def dfs(i):
+            if states[i] == VISITING:
+                return False
+            elif states[i] == VISITED:
+                return True
+            states[i] = VISITING
+
+            for nei in g[i]:
+                if not dfs(nei):
+                    return False
+
+            states[i] = VISITED
+            order.append(i)
+            return True
+
+        
+        for i in range(numCourses):
+            if not dfs(i):
+                return []
+        
+        return order # Time: O(V + E), Space: O(V + E)
+