114. 二叉树展开为链表

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution:
    def flatten(self, root):
        while root:
            if root.left==None:
                root=root.right
            else:
                total=root.left
                while total.right!=None:
                    total=total.right
                total.right=root.right
                root.right=root.left
                root.left=None
                root=root.right
#将左子树插入到右子树的地方
#将原来的右子树接到左子树的最右边节点
#考虑新的右子树的根节点，一直重复上边的过程，直到新的右子树为 null