从零开始的LC刷题(23): Maximum Depth of Binary Tree 二叉树深度

原题：

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.

求二叉树深度只要dfs就好了，每个节点求左右子树最大值并返回最大值+1，结果：

Success

Runtime: 8 ms, faster than 98.23% of C++ online submissions for Maximum Depth of Binary Tree.

Memory Usage: 19.1 MB, less than 93.50% of C++ online submissions for Maximum Depth of Binary Tree.

代码：

/** * 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;} int l=maxDepth(root->left); int r=maxDepth(root->right); if (l>=r){return l+1;} else return r+1; } };