Question

Given a string, return the first recurring character in it, or “None” if there is no recurring character.

Answer 1

Example:

input = "interviewquery"

output = "i"

Given that we have to return the first index of the second repeating character, we should be able to go through the string in one loop, save each unique character, and then just check if the character exists in that saved set. If it does, return the character.