Find largest value in each tree row

Tree Depth-First Search Breadth-First Search Binary Tree

66.3% acceptance

Feb 19, 2026

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130

Given the root of a binary tree, return an array of the largest value in each row of the tree (0-indexed).

Solution

Rust

Time O(n²)

Space O(n)

LeetCode

solution.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::rc::Rc;
use std::cell::RefCell;
use std::collections::VecDeque;
impl Solution {
  pub fn largest_values(root: Option<Rc<RefCell<TreeNode>>>) -> Vec<i32> {
    let mut result = Vec::new();
    let mut queue = VecDeque::new();
    if let Some(r) = root { queue.push_back(r); }
    while !queue.is_empty() {
      let size = queue.len();
      let mut max_val = i32::MIN;
      for _ in 0..size {
        let node = queue.pop_front().unwrap();
        let nb = node.borrow();
        if nb.val > max_val { max_val = nb.val; }
        if let Some(l) = nb.left.clone() { queue.push_back(l); }
        if let Some(r) = nb.right.clone() { queue.push_back(r); }
      }
      result.push(max_val);
    }
    result
  }
}