Solve : Course Schedule

Author: printjin-gmailcom

course-schedule/printjin-gmailcom.py

@@ -0,0 +1,23 @@
+class Solution:
+    def canFinish(self, numCourses, prerequisites):
+        from collections import defaultdict
+        graph = defaultdict(list)
+        for a, b in prerequisites:
+            graph[b].append(a)
+        visited = [0] * numCourses  
+        def dfs(course):
+            if visited[course] == 1:
+                return False  
+            if visited[course] == 2:
+                return True   
+            visited[course] = 1  
+            for next_course in graph[course]:
+                if not dfs(next_course):
+                    return False
+            visited[course] = 2  
+            return True
+        for course in range(numCourses):
+            if not dfs(course):
+                return False
+        
+        return True