LeetCode 865. Smallest Subtree with all the Deepest Nodes

Problem Statement

// Definition for a binary tree node.
// #[derive(Debug, PartialEq, Eq)]
// pub struct TreeNode {
//   pub val: i32,
//   pub left: Option<Rc<RefCell<TreeNode>>>,
//   pub right: Option<Rc<RefCell<TreeNode>>>,
// }
// 
// impl TreeNode {
//   #[inline]
//   pub fn new(val: i32) -> Self {
//     TreeNode {
//       val,
//       left: None,
//       right: None
//     }
//   }
// }
use std::rc::Rc;
use std::cell::RefCell;
impl Solution {
    fn get_max_depth(root: Option<Rc<RefCell<TreeNode>>>) -> i32 {
        if let Some(node) = root {
            return std::cmp::max(Self::get_max_depth(RefCell::borrow(&node).left.clone()),
                                 Self::get_max_depth(RefCell::borrow(&node).right.clone())) + 1;
        } else {
            return 0;
        }
    }

    pub fn subtree_with_all_deepest(root: Option<Rc<RefCell<TreeNode>>>) -> Option<Rc<RefCell<TreeNode>>> {
        if let Some(node) = root {
            let diff = Self::get_max_depth(RefCell::borrow(&node).left.clone()) -
                Self::get_max_depth(RefCell::borrow(&node).right.clone());
            if diff == 0 {
                return Some(node);
            } else if diff > 0 {
                return Self::subtree_with_all_deepest(RefCell::borrow(&node).left.clone());
            } else {
                return Self::subtree_with_all_deepest(RefCell::borrow(&node).right.clone());
            }
        } else {
            return root;
        }
    }
}