【LeetCode & 剑指offer 刷题笔记】目录（持续更新中...）
104. 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.
Note: A leaf is a node with no children.
Example:
Given binary tree [3,9,20,null,null,15,7],
3
/
9 20
/
15 7
return its depth = 3.
/**
* 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 == NULL) return 0; //递归的出口
int depth_left = maxDepth(root->left); //用递归的方法，左子树的深度
int depth_right = maxDepth(root->right); //右子树的深度
return 1 + max(depth_left, depth_right);
}
};