Univalued binary tree

Tree Depth-First Search Breadth-First Search Binary Tree

72.9% acceptance

Feb 27, 2026

1977

A binary tree is uni-valued if every node in the tree has the same value. Given the root of a binary tree, return true if the given tree is uni-valued, or false otherwise.

Solution

Rust

Time O(n)

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;
impl Solution {
  pub fn is_unival_tree(root: Option<std::rc::Rc<std::cell::RefCell<TreeNode>>>) -> bool {
    fn check(node: &Option<std::rc::Rc<std::cell::RefCell<TreeNode>>>, val: i32) -> bool {
      match node { None => true, Some(n) => { let n = n.borrow(); n.val == val && check(&n.left, val) && check(&n.right, val) } }
    }
    match &root { None => true, Some(n) => check(&root, n.borrow().val) }
  }
}