LeetCode 104. Maximum Depth of Binary Tree

原题链接在这里：https://leetcode.com/problems/maximum-depth-of-binary-tree/

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.

题解：

左右最大深度+1记为当前node maximum depth.

终止条件是root == null, 返回0.

Time Complexity: O(n), n is the number of nodes in the tree. Space: O(logn).

AC Java:

 1 /**
 2  * Definition for a binary tree node.
 3  * public class TreeNode {
 4  *     int val;
 5  *     TreeNode left;
 6  *     TreeNode right;
 7  *     TreeNode(int x) { val = x; }
 8  * }
 9  */
10 public class Solution {
11     public int maxDepth(TreeNode root) {
12         if(root == null){
13             return 0;
14         }
15         return Math.max(maxDepth(root.left), maxDepth(root.right)) + 1;
16     }
17 }

AC JavaScript:

 1 /**
 2  * Definition for a binary tree node.
 3  * function TreeNode(val) {
 4  *     this.val = val;
 5  *     this.left = this.right = null;
 6  * }
 7  */
 8 /**
 9  * @param {TreeNode} root
10  * @return {number}
11  */
12 var maxDepth = function(root) {
13     if(!root){
14         return 0;
15     }
16     
17     return Math.max(maxDepth(root.left), maxDepth(root.right)) + 1;
18 };

AC C++:

 1 /**
 2  * Definition for a binary tree node.
 3  * struct TreeNode {
 4  *     int val;
 5  *     TreeNode *left;
 6  *     TreeNode *right;
 7  *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 8  *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 9  *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
10  * };
11  */
12 class Solution {
13 public:
14     int maxDepth(TreeNode* root) {
15         if(!root){
16             return 0;
17         }
18 
19         return 1 + max(maxDepth(root->left), maxDepth(root->right));
20     }
21 };

AC Python:

 1 # Definition for a binary tree node.
 2 # class TreeNode:
 3 #     def __init__(self, val=0, left=None, right=None):
 4 #         self.val = val
 5 #         self.left = left
 6 #         self.right = right
 7 class Solution:
 8     def maxDepth(self, root: Optional[TreeNode]) -> int:
 9         if not root:
10             return 0
11         return 1 + max(self.maxDepth(root.left), self.maxDepth(root.right))

跟上Balanced Binary Tree, Minimum Depth of Binary Tree, Diameter of Binary Tree, Smallest Subtree with all the Deepest Nodes, Height of Binary Tree After Subtree Removal Queries.

posted @ 2015-09-05 00:49  Dylan_Java_NYC  阅读(241)  评论(0)  编辑  收藏  举报