TL;DR

On with Advent of Code puzzle 11 from 2016: parsing the inputs.

In this first practical post we will take a look at the inputs and how to parse them.

Inputs

The example input in the first part of the puzzle is the following:

The first floor contains a hydrogen-compatible microchip and a lithium-compatible microchip.
The second floor contains a hydrogen generator.
The third floor contains a lithium generator.
The fourth floor contains nothing relevant.

For completeness, this is the specific input I have:

The first floor contains a promethium generator and a promethium-compatible microchip.
The second floor contains a cobalt generator, a curium generator, a ruthenium generator, and a plutonium generator.
The third floor contains a cobalt-compatible microchip, a curium-compatible microchip, a ruthenium-compatible microchip, and a plutonium-compatible microchip.
The fourth floor contains nothing relevant.

In addition, part 2 requires to put additional stuff on the first floor, which I eventually added at the end like the following:

The first floor contains a promethium generator and a promethium-compatible microchip.
The second floor contains a cobalt generator, a curium generator, a ruthenium generator, and a plutonium generator.
The third floor contains a cobalt-compatible microchip, a curium-compatible microchip, a ruthenium-compatible microchip, and a plutonium-compatible microchip.
The fourth floor contains nothing relevant.
The first floor contains a elerium generator and a elerium-compatible microchip.
The first floor contains a dilithium generator and a dilithium-compatible microchip.

Parsing

Each line contains an indication of the floor and a list of contained items.

To get the floor number (as text) we can use the following regular expression:

my ($floor) = m{\A The \s+ (\S+) \s+ floor \s+ contains \s+}mxs;

This floor name can then be turned into some other index using a hash.

Getting the list of elements can be trickier because it’s not known how many of the are there. I resorted to the trick of taking a match and deleting it at the same time, until there’s no more left.

Hence, for microchips:

while (s{(\S+)-compatible}{}mxs) {
    # element name now in $1
    ...
}

Something similar, for generators:

while (s{(\S+) \s+ generator}{}mxs) {
    # element name now in $1
    ...
}

Having multiple lines referring to the contents of a floor is not a problem with this approach, as long as we use the information extracted about the floor for each line to fill in our data structures.

This is it!

As the title implies, this is it for today. In the next post, we’ll be looking at the (initial) data structure where we will fit the parsed data… so until then take care and stay safe!