100. Same tree 一个击败了100%C++用户的代码-编程知识

100. Same tree 一个击败了100%C++用户的代码

题目描述

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

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

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

Constrains:

The number of nodes in both trees is in the range [0,100].
$10^4<=Node.val<=10^4$

解答思路

使用递归判断。首先两棵树都是空的时候，是相等的。然后只有一个是空的，是不相等的。最后就是都不为空就判断节点的值相不相等。

/*** Definition for a binary tree node.* struct TreeNode {*     int val;*     TreeNode *left;*     TreeNode *right;*     TreeNode() : val(0), left(nullptr), right(nullptr) {}*     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}*     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}* };*/
class Solution {
public:bool isSameTree(TreeNode* p, TreeNode* q) {if(p == nullptr && q == nullptr){return true;}  else if(p == nullptr || q == nullptr){return false;}else if(p->val != q ->val){return false;}else{return isSameTree(p->left, q->left) && isSameTree(p->right, q->right);}}
};