LeetCode: 100. Same Tree

题目

原题地址:https://leetcode.com/problems/same-tree/

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:

image

Input: p = [1,2,3], q = [1,2,3]
Output: true

Example 2:

image2

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

Example 3:

image3

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

解法

从上到下一层一层进行比较。

这个方法的 Python 代码类似下面这样:

# Definition for a binary tree node.
# class TreeNode(object):
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution(object):
    def isSameTree(self, p, q):
        return self.is_same(p, q)

    def is_same(self, a, b):
        if a is None and b is None:
            return True
        if a is None or b is None:
            return False
        if a.val != b.val:
            return False

        return self.is_same(a.left, b.left) and self.is_same(a.right, b.right)

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