Day 06

• Problem description

Cephalopod maths…

Tips for first problem

1. Pretty straightforward parsing problem. Read in the input file line by line, and split each line into tokens (numbers and operators). I used split after readdlm to get a matrix of strings.

2. You can accrue sum with an if statement inside a loop. Keep track of the current operation (either + or *), and when you hit a blank line, add the current chunk to the total sum and reset the chunk. (I thought mapreduce might be useful, but it was more complicated than just a loop with an if statement.)

Second problem

• Same idea - but more tricky as the parsing is now harder.

• One trick I used was to transpose the matrix of strings, so that each row corresponds to a column in the input file. This way, I could easily iterate over each line and process the tokens. In a first version I tried to accrue data for each “chunk” in a vector, but that got complicated quickly. So I ended up looping over and keeping track of the current operation and chunk value with global variables.

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Also, I over-wrote the original solution.jl file … so only code for Part 2 is available here. And it needs some refactoring and cleaning up!

Code

Julia solution

Julia code / solution for the first part of that problem (simpler version of the code ended up as solution for B!).

Second part solution of that problem.