【LeetCode OJ】Same Tree

Problem Link:

https://oj.leetcode.com/problems/same-tree/

The following recursive version is accepted but the iterative one is not accepted...

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

class Solution:
    # @param p, a tree node
    # @param q, a tree node
    # @return a boolean
    def isSameTree(self, p, q):
        """
        Check both trees level by level using BFS
        """
        if not p or not q:
            return p == q
        if p.val == q.val:
            return self.isSameTree(p.left, q.left) and self.isSameTree(p.right, q.right)
        else:
            return False