100. Same Tree

Easy LeetCode

Given the roots of two binary trees p and q, 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: p = [1,2,3], q = [1,2,3]

Output: true

Example 2

Input: p = [1,2], q = [1,null,2]

Output: false

Example 3

Input: p = [1,2,1], q = [1,1,2]

Output: false

Constraints

• The number of nodes in both trees is in the range [0, 100]
• -104 <= Node.val <= 104

How to solve the problem

Code

• Recursion

# 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: Optional[TreeNode], q: Optional[TreeNode]) -> bool:
        if p is None or q is None:
            return p is q
        # current node equal or not; left node equal or not; right node equal or not
        return p.val == q.val and self.isSameTree(p.left, q.left) and self.isSameTree(p.right, q.right)

Complexity

• Time complexity: O(n), n == number of nodes
• Space complexity: O(n)