class Solution:
    def increasingBST(self, root: TreeNode) -> TreeNode:
        def recursion(root):
            
            if not root:
                return
            
            recursion(root.left)

            # self.thisNode = TreeNode(root.val)
            root.left = None
            if not self.lastNode:
                self.lastNode = root
                self.head = root
            else:
                self.lastNode.right = root
                self.lastNode = root
            
            recursion(root.right)

        self.lastNode = None     
        self.head = None

        recursion(root)
        return self.head

树 简单 每日一题 做过的

https://leetcode-cn.com/problems/increasing-order-search-tree/