# AoC 2018 Day 5: Alchemical reduction

### Source: Alchemical Reduction

Part 1:Given a string, reduce it by removing pairs of letters that are the same letter but different cases. Repeat until you have a minimal string.

Part 1:Given a string, reduce it by removing pairs of letters that are the same letter but different cases. Repeat until you have a minimal string.

Part 1:Given a log of guard shifts and times asleep/awake, calculate the guard that was asleep most often and which minute they were most asleep for.

Part 1:Given a list of overlapping regions defined by (left, top, width, height) count how many integer points occur in more than one region.

Part 1:Given a list of strings, count how many contain exactly two of a letter (`a`

) and how many contain exactly three of a letter (`b`

). Calculate`a*b`

.

Part 1:Given a list of numbers (positive and negative) calculate the sum.

Let’s do it again! I’m starting a day late, but much better than last year ðŸ˜„!

This time around, I’m hoping to solve each problem in both Python and Racket, both to show an example of how the languages differ and … well, because I can ðŸ˜‡.

*EDIT 2018-12-05*: Yeah… I’m not actually going to do these in both Racket and Python. The solutions are ending up being near direct translations. Since there are probably fewer people solving these in Racket, I’ll do that first and Python eventuallyâ„¢.

As always, these problems are wonderful to try to solve yourself. If you agree, *stop reading now*. This post isn’t going anywhere.

If you’d like to see the full form of any particular solution, you can do so on GitHub (including previous years and possibly some I haven’t written up yet): jpverkamp/advent-of-code

As I did with last year / yesterday, I’ve written up a series of posts for the Advent of Code 2017 problems. Again, I didn’t manage to write them up as I did them, but this time around I least I finished mostly on time.

As I did last year, I’m going to solve the Advent of Code problems again this year.

Or that was the plan. It turns out that instead I put down my blog for almost a year and a half and never quite got around to doing these problems. So I’m actually backdating these posts from the early days of 2018 to where they would have been had I solved them on time. They’re still interesting problems, so give them a read.

Part 1:Implement a Turing machine defined as such:`Begin in state A. Perform a diagnostic checksum after 6 steps. In state A: If the current value is 0: - Write the value 1. - Move one slot to the right. - Continue with state B. If the current value is 1: - Write the value 0. - Move one slot to the left. - Continue with state B. ...`

What is the final number of

`1s`

on the tape?

Part 1:Given a series of reversible components of the form`3/4`

(can connect a`3`

on one end to a`4`

on the other), form a bridge of components. The bridge’s strength is equal to the sum of component values. So`0/3, 3/7, and 7/4`

has a strength of`0+3 + 3+7 + 7+4 = 24`

.What is the strongest possible bridge?