【leetcode刷题】T117-二叉树的最大深度

示例：
给定二叉树 [3,9,20,null,null,15,7]，
    3
   / \
  9  20
    /  \
   15   7
返回它的最大深度 3 。

# Definition for a binary tree node.
# class TreeNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution(object):
    def maxDepth(self, root):
        """
        :type root: TreeNode
        :rtype: int
        """
        return self.get_max_depth(root, 0)

    def get_max_depth(self, node, depth):
        if not node:
            return depth
        return max(self.get_max_depth(node.left, depth+1), self.get_max_depth(node.right, depth+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) {
        return get_max_depth(root, 0);
    }

    int get_max_depth(TreeNode* node, int depth){
        if(!node)
            return depth;
        return max(get_max_depth(node->left, depth + 1), get_max_depth(node->right, depth + 1));
    }
};