class Solution{
    public:
        int LengthOfLongestSubString(string s){
            int n = s.length();
            int maxlen = 0;
            unordered_set<char> charset;
            int left = 0;

            for(int right = 0;right<n;right++){
                if(charset.count(s[right])==0){
                    charset.insert(s[right]);
                    maxlen = max(maxlen, right-left+1);
                }while(charset.count(s[right])){
                    charset.erase(s[left]);
                    left++;
                }
            }
            return maxlen;


        }
}