Time: 5 ms (60.55%), Space: 19.2 MB (26.46%) - LeetHub

Author: shinecoding

0207-course-schedule/0207-course-schedule.py

@@ -0,0 +1,27 @@
+class Solution:
+    def canFinish(self, numCourses: int, prerequisites: List[List[int]]) -> bool:
+        preMap = defaultdict(list)
+        visitSet = set()
+
+        for pre, cur in prerequisites:
+            preMap[cur].append(pre)
+
+        def dfs(crs):
+            if crs in visitSet:
+                return False
+            if preMap[crs] == []:
+                return True
+
+            visitSet.add(crs)
+            for pre in preMap[crs]:
+                if not dfs(pre): 
+                    return False
+            visitSet.remove(crs)
+            preMap[crs] = []
+            return True
+            
+        for crs in range(numCourses):
+            if not dfs(crs):
+                return False
+        return True
+