104. Maximum Depth of Binary Tree

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

Rust Solution

struct Solution;
use rustgym_util::*;

trait MaxDepth {
    fn max_depth(&self) -> i32;
}

impl MaxDepth for TreeLink {
    fn max_depth(&self) -> i32 {
        if let Some(node) = self {
            let node = node.borrow();
            return 1 + i32::max(node.left.max_depth(), node.right.max_depth());
        }
        0
    }
}

impl Solution {
    fn max_depth(root: TreeLink) -> i32 {
        root.max_depth()
    }
}

#[test]
fn test() {
    let p = tree!(3, tree!(9), tree!(20, tree!(15), tree!(7)));
    assert_eq!(Solution::max_depth(p), 3);
}

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