Question

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

Solution

# 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
        """
        if p is None and q is None:
            return True
        elif p is not None and q is not None:
            l = [(p, q)]
            while True:
                try:
                    (pnode, qnode) = l[-1]
                    del l[-1]
                    if pnode.val != qnode.val:
                        return False
                    if self.isSameStructure(pnode, qnode):
                        if pnode.left is not None:
                            l.append((pnode.left, qnode.left))
                        if pnode.right is not None:
                            l.append((pnode.right, qnode.right))
                    else:
                        return False
                except IndexError:
                    return True
        else:
            return False

    def isSameStructure(self, p, q):
        if bool(p.left) != bool(q.left) or bool(p.right) != bool(q.right):
            return False
        else:
            return True