LeetCode 1120. Maximum Average Subtree

Problem Statement

use std::rc::Rc;
use std::cell::RefCell;
use std::borrow::Borrow;

impl Solution {
    fn dfs(root: Option<&Rc<RefCell<TreeNode>>>, ans: &mut f64) -> (i32, i32) {
        if let Some(node) = root {
            let (l, r) = (Self::dfs(RefCell::borrow(&node).left.as_ref(), ans),
                          Self::dfs(RefCell::borrow(&node).right.as_ref(), ans));
            let sum = l.0 + r.0 + RefCell::borrow(&node).val;
            let total = 1 + l.1 + r.1;
            let avg = sum as f64 / total as f64;
            if avg > *ans {
                *ans = avg;
            }
            return (sum, total);
        } else {
            return (0, 0);
        }
    }

    pub fn maximum_average_subtree(root: Option<Rc<RefCell<TreeNode>>>) -> f64 {
        let mut ans = 0.;
        if root.is_none() {
            return ans;
        }
        Self::dfs(Some(&root.unwrap()), &mut ans);
        return ans;
    }
}