leetcode: finished #210

content/leetcode/2023/8.md

@@ -3,6 +3,52 @@ title: "2023.8"
 draft: false
 ---
 
+# 2023.8.17
+
+```python
+#
+# @lc app=leetcode.cn id=210 lang=python3
+#
+# [210] 课程表 II
+#
+
+# @lc code=start
+from typing import List
+
+
+class Solution:
+    def findOrder(self, numCourses: int, prerequisites: List[List[int]]) -> List[int]:
+        # 0: unvisited, 1: visiting, 2: visited
+        visited = [0] * numCourses
+        # graph[i]: list of courses that require course i
+        graph = [[] for _ in range(numCourses)]
+        for x, y in prerequisites:
+            graph[x].append(y)
+
+        ans = []
+
+        def dfs(i: int) -> bool:
+            if visited[i] == 1:
+                return False
+            if visited[i] == 2:
+                return True
+            visited[i] = 1
+            for j in graph[i]:
+                if not dfs(j):
+                    return False
+            visited[i] = 2
+            ans.append(i)
+            return True
+
+        for i in range(numCourses):
+            if not dfs(i):
+                return []
+        return ans
+
+
+# @lc code=end
+```
+
 # 2023.8.16
 
 ```python