Leetcode 104. Maximum Depth of Binary Tree

文章作者：Tyan
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1. Description

2. Solution

• Version 1

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    int maxDepth(TreeNode* root) {
        int maxDepth = 0;
        preorderTraverse(root, 0, maxDepth);
        return maxDepth;
    }
    
private:
    void preorderTraverse(TreeNode* root, int depth, int& maxDepth) {
        if(!root) {
            return;
        }
        depth++;
        if(depth > maxDepth) {
            maxDepth = depth;
        }
        preorderTraverse(root->left, depth, maxDepth);
        preorderTraverse(root->right, depth, maxDepth);
    }
};

• Version 2

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    int maxDepth(TreeNode* root) {
        if(!root) {
            return 0;
        }
        return max(maxDepth(root->left), maxDepth(root->right)) + 1;
    }
};

Reference

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