Given a string S, return the number of substrings of length K with no repeated characters. Example 1: Input: S = "havefunonleetcode", K = 5 Output: 6 Explanation: There are 6 substrings they are : 'havef','avefu','vefun','efuno','etcod','tcode'. Example 2: Input: S = "home", K = 5 Output: 0 Explanation: Notice K can be larger than the length of S. In this case is not possible to find any substring. Note: 1 <= S.length <= 10^4 All characters of S are lowercase English letters. 1 <= K <= 10^4