class Solution {
    public int lengthOfLongestSubstring(String s) {
        HashMap<Character,Integer> map = new HashMap<>();
        
        int res = 0, i = 0,left=0;
        
        while(i<s.length())
        {
            char ch = s.charAt(i);
            if(map.containsKey(ch) && map.get(ch)>=left) left = map.get(ch)+1;
            else res = Math.max(res,i-left+1);
            map.put(ch,i++);
        }
        return res;
    }
}