feat: [Week 10-3] solve course schedule

Author: Chaedie

course-schedule/Chaedie.py

@@ -0,0 +1,39 @@
+"""
+(해설을 보면서 따라 풀었습니다.)
+
+Solution: graph 에서 circular 가 생기면 false, 아니면 true
+
+n: numCourses
+p: number of preRequisites
+Time: O(n + p) 
+Space: O(n + p)
+"""
+
+
+class Solution:
+    def canFinish(self, numCourses: int, prerequisites: List[List[int]]) -> bool:
+        graph = {i: [] for i in range(numCourses)}
+        for crs, pre in prerequisites:
+            graph[crs].append(pre)
+
+        traversing = set()
+        finished = set()
+
+        def dfs(crs):
+            if crs in traversing:
+                return False
+            if crs in finished:
+                return True
+
+            traversing.add(crs)
+            for pre in graph[crs]:
+                if not dfs(pre):
+                    return False
+            traversing.remove(crs)
+            finished.add(crs)
+            return True
+
+        for crs in graph:
+            if not dfs(crs):
+                return False
+        return True