0100-Same-Tree.py

'''
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:
#     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:
        if not p and not q:
            return True
        elif not p or not q:
            return False
        return p.val == q.val and self.isSameTree(p.left, q.left) and self.isSameTree(p.right, q.right)

    def isSameTree_iterative(self, p: TreeNode, q: TreeNode) -> bool:
        stack = [(p, q)]
        while stack:
            node1, node2 = stack.pop()
            if not node1 and not node2:
                continue
            elif not node1 or not node2:
                return False
            if node1.val != node2.val:
                return False
            stack.append((node1.right, node2.right))
            stack.append((node1.left, node2.left))
        return True