struct Solution;
impl Solution {
pub fn is_valid(s: String) -> bool {
let s = s.into_bytes();
let mut st = vec![];
for x in s {
if matches!(st.last(), Some(y) if x - y == 2 || x - y == 1) {
st.pop();
} else {
st.push(x);
}
st.is_empty()
fn main() {