AOC 2022 — Day 6

In this article, I’ll present my solution for the day 6 of the Advent of Code 2022

You can find here my solutions for the previous challenges : Day 1, Day 2, Day 3, Day 4, Day 5

https://adventofcode.com/2022/day/6

The expedition is ready to make their way toward the star fruit grove. One of the elves gives you a handheld device. This device has many fancy features, but your first focus is the communication system.

As you’re experienced with this kind of system, the elf convinced the others that they could give you the broken device.

To fix the communication system, you need to implement a subroutine able to decrypt the datastream.

Part 1

For the first part of this challenge, the goal is to identify that start-of-packet marker.

In the protocol used by the elves, the start-of-packet marker is indicated by a sequence of four characters that are all different.

Input

The input you receive is a simple string. If we take the following example :

mjqjpqmgbljsphdztnvjfqwrcgsmlb

• The first 4 characters are mjqj, the j is there twice so that’s not the marker
• The next 4 are jqjp, j is still there twice
• Then it’s qjpq, q is present twice, so that’s not…