647-Palindromic-Substrings.rs

impl Solution {
    pub fn count_substrings(s: String) -> i32 {
        let s = s.chars().collect::<Vec<char>>();
        let (mut count, length): (i32, i32) = (0, s.len() as i32);

        for i in 0..length {
            // odd length

            let (mut l, mut r) = (i, i);
            while l >= 0 && r < length && s[l as usize] == s[r as usize] {
                count += 1;
                l -= 1;
                r += 1;
            }

            // even length

            let (mut l, mut r) = (i, i + 1);

            while l >= 0 && r < length && s[l as usize] == s[r as usize] {
                count += 1;
                l -= 1;
                r += 1;
            }
        }

        count
    }
}