same-tree.py

# -*- coding:utf-8 -*-


# Given two binary trees, write a function to check if they are the same or not.
#
# Two binary trees are considered the same if they are structurally identical and the nodes have the same value.
#
# Example 1:
#
#
# Input:     1         1
#           / \       / \
#          2   3     2   3
#
#         [1,2,3],   [1,2,3]
#
# Output: true
#
#
# Example 2:
#
#
# Input:     1         1
#           /           \
#          2             2
#
#         [1,2],     [1,null,2]
#
# Output: false
#
#
# Example 3:
#
#
# Input:     1         1
#           / \       / \
#          2   1     1   2
#
#         [1,2,1],   [1,1,2]
#
# Output: false
#
#


# 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 isSameTree(self, p, q):
        """
        :type p: TreeNode
        :type q: TreeNode
        :rtype: bool
        """
        stack = [(p, q)]
        while stack:
            node1, node2 = stack.pop()
            if not node1 and not node2:
                continue
            if None in (node1, node2) or node1.val != node2.val:
                return False
            if node1.val == node2.val:
                stack.append((node1.left, node2.left))
                stack.append((node1.right, node2.right))
        
        return True