二叉树展开为链表-二叉树114-python

算法思想：

python

class TreeNode:
    def __init__(self, val=0, left=None, right=None):
        self.val = val
        self.left = left
        self.right = right

class Solution:
    def flatten(self, root: TreeNode) -> None:
        """
        Do not return anything, modify root in-place instead.
        """
        if not root:
            return
        
        self.flatten(root.left)
        self.flatten(root.right)

        left = root.left
        right = root.right

        root.right = left
        root.left = None

        p = root
        while(p.right != None):
            p = p.right
        
        p.right = right