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