※ 引述《dont (dont)》之銘言： : 1110. Delete Nodes And Return Forest : ## 思路 : DFS掃整個Tree : 如果node沒有parent且不在to_delete就加到res : ## Complexity : Time, Space: O(N) : ## Code : ```python : class Solution: : def delNodes(self, root: Optional[TreeNode], to_delete: List[int]) -> : List[TreeNode]: : to_delete = set(to_delete) : res = [] : def dfs(node, has_parent): : if not node: : return : if node.val not in to_delete and has_parent is False: : res.append(node) : has_parent = False if node.val in to_delete else True : if node.left: : dfs(node.left, has_parent) : if node.left.val in to_delete: : node.left = None : if node.right: : dfs(node.right, has_parent) : if node.right.val in to_delete: : node.right = None : dfs(root, False) : return res : ``` 思路: 找到to_delete的值 找到且有left or right就加到result Python Code: class Solution: def delNodes(self, root: Optional[TreeNode], to_delete: List[int]) -> List[TreeNode]: res = [] def dfs(root, is_root): if not root: return None root_deleted = root.val in to_delete if is_root and not root_deleted: res.append(root) root.left = dfs(root.left, root_deleted) root.right = dfs(root.right, root_deleted) return None if root_deleted else root dfs(root, True) return res -- ※ 發信站: 批踢踢實業坊(ptt-website.tw), 來自: 123.194.160.111 (臺灣) ※ 文章網址: https://ptt-website.tw/Marginalman/M.1721183019.A.D28

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