class Solution {
public:
    int lengthOfLongestSubstring(string s) 
    {
        if (s.size() == 0) return 0;
        int maxLen = 0;
        vector<int> index(256,-1);
        for (int i=0,j = 0; j < s.size(); j++)
        {
            i = max(index[s[j]]+1,i);
            maxLen = max(maxLen,j-i+1);
            index[s[j]] = j;
        }

        return maxLen;
    }
};

class Solution {
        public int lengthOfLongestSubstring(String s) 
        {
               if(s==null || s.length()==0) return 0;
               int[] index=new int[256];
               Arrays.fill(index,-1);
               int maxLen=0;
               for(int i=0,j=0;j<s.length();j++)
               {
                   i=Math.max(index[s.charAt(j)]+1,i);
                   maxLen=Math.max(maxLen,j-i+1);
                   index[s.charAt(j)]=j;
               }
               
               return maxLen;
        }
    }