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230.kth-smallest-element-in-a-bst.rs
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230.kth-smallest-element-in-a-bst.rs
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/*
* @lc app=leetcode id=230 lang=rust
*
* [230] Kth Smallest Element in a BST
*/
// @lc code=start
// 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 {
pub fn kth_smallest(mut root: Option<Rc<RefCell<TreeNode>>>, k: i32) -> i32 {
if root.is_none() { return 0; }
let mut nodes = vec![];
while let Some(rc_node) = root {
nodes.push(Some(rc_node.clone()));
root = rc_node.borrow().left.clone();
}
let mut i = 0;
loop {
root = nodes.pop().unwrap();
i += 1;
if i == k {
let val = root.unwrap().borrow().val;
return val;
}
root = root.unwrap().borrow().right.clone();
while let Some(rc_node) = root {
nodes.push(Some(rc_node.clone()));
root = rc_node.borrow().left.clone();
}
}
return 0;
}
}
// @lc code=end