802

Author: ProHiryu

DFS/traditionalDFS/802.md

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+## Find Eventual Safe States
+
+#### Description
+
+[link](https://leetcode.com/problems/find-eventual-safe-states/)
+
+---
+
+#### Solution
+
+- See Code
+
+---
+
+#### Code
+
+> 最坏情况：O(n^2)
+
+```python
+class Solution:
+    def eventualSafeNodes(self, graph: List[List[int]]) -> List[int]:
+        visited = [-1 for _ in range(len(graph))]
+        res = []
+        
+        def dfs(i):
+            # 暂时定位为不安全节点，等到循环结束改为安全节点
+            visited[i] = 0
+            for j in graph[i]:
+                # 如果找到已经访问过的不安全节点，说明有环，直接返回
+                if visited[j] == 0 or (visited[j] == -1 and dfs(j)):
+                    return True
+            # 已经访问并且确认为安全节点
+            visited[i] = 1
+            res.append(i)
+            return False
+        
+        for i in range(len(graph)):
+            if visited[i] == -1:
+                dfs(i)
+        return sorted(res)
+```