Given a binary tree, flatten it to a linked list in-place.

FALTTEN.py

__author__ = 'Vivek'

#Given a binary tree, flatten it to a linked list in-place.

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

class Solution:
    # @param A : root node of tree
    # @return the root node in the tree
    def rightMost(self, x) :
        p = x
        while p.right != None :
            p = p.right
        return p

    def helper(self, root) :
        if root == None :
            return root
        if root.left and root.right :
            x = self.helper(root.left)
            rm = self.rightMost(x)
            y = self.helper(root.right)
            root.left = None
            root.right = x
            rm.right = y
            rm.left = None
        elif root.left :
            x = self.helper(root.left)
            root.left = None
            root.right = x
        else :
            x = self.helper(root.right)
            root.left = None
            root.right = x
        return root

    def flatten(self, A):
        if A == None :
            return None
        else :
            return self.helper(A)