README_EN.md

104. Maximum Depth of Binary Tree

中文文档

Description

Given the root of a binary tree, return its maximum depth.

A binary tree's maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node.

 

Example 1:

Input: root = [3,9,20,null,null,15,7]

Output: 3

Example 2:

Input: root = [1,null,2]

Output: 2

Example 3:

Input: root = []

Output: 0

Example 4:

Input: root = [0]

Output: 1

 

Constraints:

• The number of nodes in the tree is in the range [0, 104].
• -100 <= Node.val <= 100

Solutions

Python3

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution:
    def maxDepth(self, root: TreeNode) -> int:
        if root is None:
            return 0
        l = self.maxDepth(root.left)
        r = self.maxDepth(root.right)
        return 1 + max(l, r)

Java

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode() {}
 *     TreeNode(int val) { this.val = val; }
 *     TreeNode(int val, TreeNode left, TreeNode right) {
 *         this.val = val;
 *         this.left = left;
 *         this.right = right;
 *     }
 * }
 */
class Solution {
    public int maxDepth(TreeNode root) {
        if (root == null) return 0;
        int l = maxDepth(root.left);
        int r = maxDepth(root.right);
        return 1 + Math.max(l, r);
    }
}

C++

class Solution {
public:
    int maxDepth(TreeNode* root) {
        if (!root) return 0;
        int l = maxDepth(root->left);
        int r = maxDepth(root->right);
        return max(l, r) + 1;
    }
};

...