Alphabetic String Calculation (Lintcode)

Problem

In the world of the moon, ordinary people will solve a problem. This problem is a string of English letters. Each time you can delete an English letter. Try to delete as few times as possible to make the various letters’ frequency appear differently. The number of deletion is the answer of the calculation that needs to be returned.

Photo by Amador Loureiro on Unsplash

Thinking about the…