參考資訊:
https://levelup.gitconnected.com/leetcode-longest-substring-without-repeating-characters-6d15c267582
題目:

解答:
use std::cmp;
impl Solution {
    pub fn length_of_longest_substring(s: String) -> i32 {
        let mut r = 0;
        let mut left = -1;
        let mut hash: Vec<i32> = vec![-1; 128];
        for (pos, ch) in s.char_indices() {
            left = cmp::max(left, hash[ch as usize]);
            hash[ch as usize] = pos as i32;
            r = cmp::max(r, (pos as i32 - left));
        }
        return r;
    }
}