invert_bin_tree

invert_bin_tree.py

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

class Solution(object):
    def swap_nodes(self, node):
        tmp = node.right
        node.right = node.left
        node.left = tmp

    def preorder(node):
        if not(node):
            return
        else:
            self.swap(node)
            preorder(node.left)
            preorder(node.right)

    def invertTree(self, root):
        """
        :type root: TreeNode
        :rtype: TreeNode
        """
        if(not(root.left or root.right)):
            return root
        else:
            #preorder traversal and swap
            self.preorder(root)