Function level_order

pub fn level_order(root: Option<Rc<RefCell<TreeNode>>>) -> Vec<Vec<i32>>

Solutions

Approach 1: BFS

• Time complexity: O(n)

• Space complexity: O(n)

• Runtime: 0 ms

• Memory: 2.6 MB

// 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;
use std::collections::VecDeque;
impl Solution {
    pub fn level_order(root: Option<Rc<RefCell<TreeNode>>>) -> Vec<Vec<i32>> {
        let mut result: Vec<Vec<i32>> = vec![];
        if root.is_none() { return result; }

        let mut deque: VecDeque<Option<Rc<RefCell<TreeNode>>>> = VecDeque::new();
        deque.push_back(root);

        while !deque.is_empty() {
            let mut current_level = vec![];
            let mut added = false;
            let level_size = deque.len();

            for _i in 0..level_size {
                let n = deque.pop_front();
                if let Some(Some(node)) = n {
                    current_level.push(node.borrow().val);
                    added = true;
                    if !node.borrow().left.is_none() { deque.push_back(node.borrow().left.clone()); }
                    if !node.borrow().right.is_none() { deque.push_back(node.borrow().right.clone()); }
                }
            }

            if !added { break; }

            result.push(current_level);
        }

        result
    }
}

Approach 2: DFS

• Time complexity: O(n)

• Space complexity: O(n)

• Runtime: 0 ms

• Memory: 2.7 MB

// 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 level_order(root: Option<Rc<RefCell<TreeNode>>>) -> Vec<Vec<i32>> {
        let mut result: Vec<Vec<i32>> = vec![];
        Self::_dfs(&mut result, root, 0);
        result
    }

    pub fn _dfs(result: &mut Vec<Vec<i32>>, root: Option<Rc<RefCell<TreeNode>>>, level: usize) {
        if let Some(node) = root {
            if result.len() == level {
                result.push(vec![node.borrow().val]);
            } else {
                result[level].push(node.borrow().val);
            }
            Self::_dfs(result, node.borrow().left.clone(), level + 1);
            Self::_dfs(result, node.borrow().right.clone(), level + 1)
        }
    }
}