LeetCode OJ

题目：

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.

解题思路：

递归求得左子树的深度left_depth，右子树的深度right_depth，则 ans = max(left_depth, right_depth) + 1;

代码：

/**
 * 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 maxDepth(TreeNode *root) {
        if (root == NULL){
            return 0;
        }
        int left_depth = maxDepth(root->left);
        int right_depth = maxDepth(root->right);
        return max(left_depth, right_depth) + 1;
        
    }
    inline int max(int a, int b) {
        return a > b ? a : b;
    }
};