BETTERCOMPRESSION - SOLUTION NEEDED Consider a string, S, that is a series of characters, each followed by its frequency as an integer

BETTERCOMPRESSION - SOLUTION NEEDED

Consider a string, S, that is a series of characters, each followed by its frequency as an integer. The string is not compressed correctly, so there may be many occurrences of the same character. A properly compressed string will consist of one instance of each character in alphabetical order followed by the total count of that character within the string.

For example, the string a3c9b2c1 has two instances where ‘c’ is followed by a count: once with 9 occurrences, and again with 1. It should be compressed to a3b2c10.

Function Description Complete the function betterCompression. The function must return the properly compressed string.

betterCompression has the following parameter: S: a string

Constraints

1 ≤ size of S ≤ 100000

‘a’ ≤ characters in S ≤ ‘z’

1 ≤ frequency of each character in S ≤ 1000

While the solution of the question is given in the website, however, I am not able to understand it. Can someone please give a hint or an idea on how to solve this question, or if there is any alternate and simpler way to do it?