104 二叉树的最大深度

https://leetcode.cn/leetbook/read/top-interview-questions-easy/xnd69e/

https://leetcode.cn/problems/maximum-depth-of-binary-tree/description/

cost: 1m42s

/**
 * 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:
    int maxDepth(TreeNode* root) {
        if (root == nullptr) {
            return 0;
        }
        int n1 = this->maxDepth(root->left);
        int n2 = this->maxDepth(root->right);
        return n1 > n2 ? n1 + 1 : n2 + 1;
    }
};

• 时间复杂度：O(n)
• 空间复杂度：O(1)