Function calculate

lcp17-nGK0Fy.rs:27–38

(s: String)

}

pub fn calculate(s: String) -> i32 {
    let mut x = 1;
    let mut y = 0;
    for c in s.chars() {
        if c == 'A' {
            x = 2 * x + y;
        } else {
            y = 2 * y + x
        }
    }
    x + y
}