class Solution:

    def lengthOfLongestSubstring(self, s: str) -> int:

        slow = 0

        fast = 0

        res_max = 0

        table = dict()

        while slow<len(s) and fast<len(s):

            if s[fast] in table:

                del(table[s[slow]])

                slow+=1

            else:

                table[s[fast]] = fast

                fast+=1

                res_max = max(res_max,fast-slow)

        return res_max

class Solution {

    public int lengthOfLongestSubstring(String s) {

        int ans = 0;

        Set occ = new HashSet();

        int n = s.length();

        int rk = -1;

        for(int i = 0;i < n; i++){

            if(i != 0){

                occ.remove(s.charAt(i - 1));

            }

            while(rk+1 < n && !occ.contains(s.charAt(rk + 1))){

                occ.add(s.charAt(rk + 1));

                ++rk;

            }

            ans = Math.max(ans,rk -i + 1);

        }

        return ans;

    }

}