LeetCode 965. Univalued Binary Tree

Problem Statement

use std::rc::Rc;
use std::cell::RefCell;
impl Solution {
    fn dfs(root: Option<&Rc<RefCell<TreeNode>>>, val: i32) -> bool {
        if let Some(n) = root {
            if RefCell::borrow(&n).val != val {
                return false;
            }
            return Self::dfs(RefCell::borrow(&n).left.as_ref(), val) &&
                   Self::dfs(RefCell::borrow(&n).right.as_ref(), val);
        } else {
            return true;
        }
    }
    pub fn is_unival_tree(root: Option<Rc<RefCell<TreeNode>>>) -> bool {
        if let Some(n) = root {
            return Self::dfs(Some(&n), RefCell::borrow(&n).val);
        } else {
            return true;
        }
    }
}