static class Solution {

public int lengthOfLongestSubstring(String s) {

Map<Character,Integer> map = new HashMap<>();

int res = 0;

int start = -1;

for(int i = 0; i < s.length(); i++){

if(map.containsKey(s.charAt(i))){

start = map.get(s.charAt(i)) > start ? map.get(s.charAt(i)) : start;

}

res = Math.max(res, i - start);

map.put(s.charAt(i), i);

}

return res;

}

}

public static void main(String[] args) {

Solution solution = new Solution();

System.out.println(solution.lengthOfLongestSubstring("abba"));

}