For this div3 problem (D), I precalculate prefix frequencies of characters (editorial code does not), and I'm still getting [TLE] ((https://mirror.codeforces.com/contest/1385/submission/114392389).

My solve function's parameters are - 1. int c (character 0 is 'a', 25 is 'z') 2. int i (starting point of substring in consideration) 3. int j (length of the substring in consideration) [ using (1<<j) ]