Count Substrings With K-Frequency Characters I

class Solution { public int numberOfSubstrings(String s, int k) { int left =0, right = 0; int hash[] = new int[26]; int count = 0; while(right<s.length()){ char c= s.charAt(right); hash[c-'a']++; while(hash[c-'a']>=k){ count = count+1 + s.length()-1-right; hash[s.charAt(left)-'a']--; left++; } right++; } return count; } }