You cannot select more than 25 topics Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
This repo is archived. You can view files and clone it, but cannot push or open issues/pull-requests.
aoc-racket/day8.rkt

58 lines
1.9 KiB
Racket

9 years ago
#lang scribble/lp2
@(require scribble/manual aoc-racket/helper)
@aoc-title[8]
9 years ago
@defmodule[aoc-racket/day8]
9 years ago
@link["http://adventofcode.com/day/8"]{The puzzle}. Our @link-rp["day8-input.txt"]{input} consists of a list of seemingly random strings within quotation marks.
@chunk[<day8>
<day8-setup>
<day8-q1>
<day8-q2>
<day8-test>]
@section{What's the difference between the literal length of the strings, and their length in memory?}
The puzzle relies the fact that within strings, certain single characters  like the backslash @litchar{\} and double-quote mark @litchar{"} — are described with more than one character. Thus, the question asks us to compare the two lengths.
The literal length of the string is trivial  use @racket[string-length]. The memory length requires interpreting a string as a Racket value, which (as seen in @secref{Day_7}) simply means using @racket[read].
@chunk[<day8-setup>
(require racket rackunit)
9 years ago
(provide (all-defined-out))
9 years ago
]
@chunk[<day8-q1>
(define (memory-length str) (string-length (read (open-input-string str))))
(define (q1 strs)
(- (apply + (map string-length strs)) (apply + (map memory-length strs))))]
9 years ago
@section{What's the difference between the re-encoded length of the literal string, and the original length?}
9 years ago
This question simply comes down to  do you know how to use the string-formatting functions in your programming language?
In Racket, a string can be re-encoded with @racket[~v]. Not a very puzzling puzzle overall.
@chunk[<day8-q2>
(define (encoded-length str) (string-length (~v str)))
(define (q2 strs)
(- (apply + (map encoded-length strs)) (apply + (map string-length strs)))) ]
@section{Testing Day 8}
@chunk[<day8-test>
(module+ test
(define input-strs (file->lines "day8-input.txt"))
(check-equal? (q1 input-strs) 1333)
(check-equal? (q2 input-strs) 2046))]