100. Same Tree

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

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

Thoughts

给两颗二叉树的root，问它们是否相同。二叉树=>分治，当前结点，左子树和右子树是否相等。或两棵树的结点一起遍历并检查是否相等。

Code

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution:
    def isSameTree(self, p: TreeNode, q: TreeNode) -> bool:
        s = [(p, q)]
        while s:
            tp, tq = s.pop()
            if not tp and not tq: continue
            elif None in [tp, tq] or tp.val != tq.val: return False       
            s.append((tp.left, tq.left))
            s.append((tp.right, tq.right))
        return True