LeetCode 1008. Construct Binary Search Tree from Preorder Traversal

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 compute(v: &Vec<i32>, start: i32, end: i32) -> Option<Rc<RefCell<TreeNode>>> {
        if start > end {
            return None;
        }
        if start == end {
            let mut node = TreeNode::new(v[start as usize]);
            return  Some(Rc::new(RefCell::new(node)))
        }
        let (mut s, mut e) = (start + 1, start + 1);
        while e <= end {
            if v[e as usize] > v[start as usize] {
                break;
            }
            e += 1;
        }
        e -= 1;
        let mut node = TreeNode::new(v[start as usize]);
        node.left = Self::compute(v, s, e);
        node.right = Self::compute(v, e + 1, end);
        Some(Rc::new(RefCell::new(node)))
    }
    pub fn bst_from_preorder(preorder: Vec<i32>) -> Option<Rc<RefCell<TreeNode>>> {
        return Self::compute(&preorder, 0, preorder.len() as i32 - 1);
    }
}