Maximum Depth of Binary Tree

Given a binary tree, find its maximum depth.

The maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node.

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Tree Depth-first Search

没啥说的，深度优先搜索(Depth-first Search)，直接在网站上敲代码，一遍AC。

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

代码效率