1110. Delete Nodes And Return Forest (Medium) - TengnanYao/daily_leetcode GitHub Wiki

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution:
    def delNodes(self, root: TreeNode, to_delete: List[int]) -> List[TreeNode]:
        self.result = []
        td = set(to_delete)
        def dfs(root, flag, isLeft, parent):
            if root:
                if root.val in td:
                    if isLeft:
                        parent.left = None
                    else:
                        parent.right = None
                    dfs(root.left, True, True, root)
                    dfs(root.right, True, False, root)
                else:
                    if flag:
                        self.result.append(root)
                    dfs(root.left, False, True, root)
                    dfs(root.right, False, False, root)
        dummy = TreeNode(left = root)
        dfs(root, True, True, dummy)
        return self.result