Compress Consecutive Characters

Problem

Given a string s, return a new string using run-length compression. Replace each group of consecutive repeated characters with the character followed by its count, but only when the count is greater than 1. The function should return the compressed string as a string.

Constraints

• 0 <= len(s) <= 10^5
• s contains only English letters and digits
• The solution should run in linear time with respect to the length of s