Leetcode 笔记 100

题目链接：Same Tree | LeetCode OJ

Given two binary trees, write a function to check if they are equal or not.

Two binary trees are considered equal if they are structurally identical and the nodes have the same value.

Tags: Depth-first Search

分析

很基本的一道深度优先遍历的题，没有太多好解释的，唯一需要注意的是leetcode约定的对结点为空的两个约定：

• left, right指向None表示没有叶子结点
• root不为None时（即结点存在），root.val不为None

示例

class Solution:
    # @param p, a tree node
    # @param q, a tree node
    # @return a boolean
    def isSameTree(self, p, q):
      if p is None and q is None:
        return True
      if p is None or q is None or p.val != q.val:
        return False
      return self.isSameTree(p.left, q.left) and self.isSameTree(p.right, q.right)

Leetcode 笔记系列的Python代码共享在https://github.com/wizcabbit/leetcode.solution

优化/简化

题目很简单，优化和简化都不会构成数量级上的影响，计算的时空复杂度都是确定的。