is_balance.rs

struct Solution;
#[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::cell::RefCell;
use std::rc::Rc;
impl Solution {
    pub fn is_balanced(root: Option<Rc<RefCell<TreeNode>>>) -> bool {
        fn check(root: Option<Rc<RefCell<TreeNode>>>) -> (bool, i32) {
            if let Some(nd) = root {
                let nd = nd.borrow();
                let (is1, d1) = check(nd.left.clone());
                let (is2, d2) = check(nd.right.clone());
                return ((d1 - d2).abs() < 2 && is1 & is2, d1.max(d2) + 1);
            }
            (true, 0)
        }
        true
    }
}

fn main() {}