[LeetCode]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.

思考：DFS。

/**
 * 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)
    {
        if(root)
        {
            return max(DFS(root->left),DFS(root->right))+1;
        }
        else return 0;
    }
    int maxDepth(TreeNode *root) {
        return DFS(root);
    }
};