Find Duplicate Characters in String

Problem

Given a string s, return all characters that appear more than once, along with how many times each duplicate character occurs. The output should preserve the order in which duplicate characters first appear in the string. Write a Python function that takes a string and returns a list of [character, count] pairs.

Constraints

• 0 <= len(s) <= 10^5
• s may contain letters, digits, spaces, or symbols
• Character comparison is case-sensitive