문제를 푼 날: 2022년 11월 13일 오후 2:05 (GMT+9)

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

Given the root of a binary tree, return its maximum depth.

A binary tree's maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node.

Example 1:

Input: root = [3,9,20,null,null,15,7]
Output: 3

Example 2:

Input: root = [1,null,2]
Output: 2

Constraints:

• The number of nodes in the tree is in the range [0, 104].
• 100 <= Node.val <= 100

Solution

/**
 * 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 travel(TreeNode* cur, int depth){
        int ret = depth;
        
        if(cur == nullptr){
            return ret;
        }
        
        if(cur->left != nullptr){
            ret = max(ret, travel(cur->left, depth+1));
        }
        
        if(cur->right != nullptr){
            ret = max(ret, travel(cur->right, depth+1));
        }
        
        return ret;
    }
    
    int maxDepth(TreeNode* root) {
        if(root == nullptr){
            return 0;
        }
        return travel(root, 1);
    }
};