Code shared from the Rust Playground

playground.rs

impl Solution {
    pub fn is_palindrome(s: String) -> bool {
        let mut chars = s
            .chars()
            .filter(|c| c.is_alphanumeric())
            .map(|c| c.to_lowercase());
        while let (Some(next), Some(next_back)) = (chars.next(), chars.next_back()) {
            if next != next_back {
                return false;
            }
        }
        // true
        (0..)
            .scan((0, 1), |acc, _| {
                *acc = (acc.1, acc.0 + acc.1);
                Some(acc.0)
            })
            .nth(n as usize)
            .unwrap()
            
        tree1.val == tree2.val &&
        is_symmetric_helper(&tree1.left, &tree2.right) &&
        is_symmetric_helper(&tree1.right, &tree2.left)

    }
}