2018-12-28

LeetCode 100. Same Tree.jpg

LeetCode 100. Same Tree

Description

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

描述

• 此题目是给定两棵树，判断两个树是否相等.
• 两颗树相等意味着结构，值要完全一样.
• 此题目使用递归求解.

# -*- coding: utf-8 -*-
# @Author:             何睿
# @Create Date:        2018-12-28 19:06:08
# @Last Modified by:   何睿
# @Last Modified time: 2018-12-28 19:12:16

class TreeNode:
    def __init__(self, x):
        self.val = x
        self.left = None
        self.right = None

class Solution:
    def isSameTree(self, p, q):
        """
        :type p: TreeNode
        :type q: TreeNode
        :rtype: bool
        """
        # 如果第一个树和第二个树都是空，说明两个树是相等的，返回True.
        if not p and not q:
            return True
        # 如果有一个数为空另一个树不为空，说明两个树一定不会相等
        if not p or not q:
            return False
        # 如果两个树的节点值不相等，则两条树不会相等，返回False
        if p.val != q.val:
            return False
        # 如果以上条件都通过了，说明两个树的当前节点相等
        # 我们分别判断这两条树的左子树是否相等，右子树是否相等
        left = self.isSameTree(p.left,q.left)
        right = self.isSameTree(p.right,q.right)
        # 返回最终结果
        return left and right

源代码文件在这里.
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