LeetCode/problems/rs/minimum-absolute-difference-in-bst.rs

// 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::cell::RefCell;
use std::cmp;
use std::rc::Rc;

struct Result {
    min: i32,
    d: i32,
    max: i32,
}

impl Solution {
    fn find_min_diff(root: Option<Rc<RefCell<TreeNode>>>) -> Result {
        match root {
            None => Result {
                min: i32::MAX,
                d: i32::MAX,
                max: i32::MIN,
            },
            Some(r) => {
                let l_min = Solution::find_min_diff(r.borrow().left.clone());
                let r_min = Solution::find_min_diff(r.borrow().right.clone());

                let mut current_d = i32::MAX;
                if l_min.max != i32::MIN {
                    current_d = (r.borrow().val - l_min.max).abs();
                }
                if r_min.min != i32::MAX {
                    current_d = cmp::min(current_d, (r_min.min - r.borrow().val).abs());
                }

                Result {
                    min: cmp::min(l_min.min, r.borrow().val),
                    d: cmp::min(cmp::min(l_min.d, r_min.d), current_d),
                    max: cmp::max(r.borrow().val, r_min.max),
                }
            }
        }
    }

    pub fn get_minimum_difference(root: Option<Rc<RefCell<TreeNode>>>) -> i32 {
        let r = Solution::find_min_diff(root);

        r.d
    }
}