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 {
    fn dfs(val: i32, root: &Option<Rc<RefCell<TreeNode>>>) -> bool {
        if root.is_none() {
            return true;
        }
        let root = root.as_ref().unwrap().borrow();
        root.val == val && Self::dfs(val, &root.left) && Self::dfs(val, &root.right)
    }
    pub fn is_unival_tree(root: Option<Rc<RefCell<TreeNode>>>) -> bool {
        let root = root.as_ref().unwrap().borrow();
        Self::dfs(root.val, &root.left) && Self::dfs(root.val, &root.right)
    }
}