闯关leetcode——100. Same Tree

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• 题目
• • 地址
  • 内容
• 解题
• • 代码地址

题目

地址

https://leetcode.com/problems/same-tree/description/

内容

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

解题

这题就是要比较两个二叉树中节点数值以及结构是否一致。需要注意的是，不能通过判断两个节点的数值一致而返回true，而是要更多考虑不一致的情况，比如左右节点结构是否一致以及数值是否一致。能够完全确认两个节点相同的就是它们都是nullptr，即都遍历到最后一级，且之前都没遇到返回false的情况。

#include <vector>
using namespace std;

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;
        if (p == nullptr || q == nullptr) return false;
        if (p->val != q->val) return false;
        return isSameTree(p->left, q->left) && isSameTree(p->right, q->right);
    }
};

代码地址

https://github.com/f304646673/leetcode/tree/main/100-Same-Tree