二叉搜索树与双向链表

class Solution:
    def Convert(self, pRootOfTree):
        # write code here
        if pRootOfTree == None:
            return None

        def find_right(node):
            while node.right:
                node = node.right
            return node

        leftNode = self.Convert(pRootOfTree.left)
        rightNode = self.Convert(pRootOfTree.right)

        retNode = leftNode

        if leftNode:
            leftNode = find_right(leftNode)
        else:
            retNode = pRootOfTree

        pRootOfTree.left = leftNode
        pRootOfTree.right = rightNode

        if leftNode != None:
            leftNode.right = pRootOfTree
        if rightNode != None:
            rightNode.left = pRootOfTree

        return retNode