Advent of Code 2020-02 with R & JavaScript

2 minute(s) read

Solving Advent of Code 2020-02 with R and JavaScript.

[Disclaimer] Obviously, this post contains a big spoiler about Advent of Code.

[Disclaimer bis] I’m no JavaScript expert so this might not be the perfect solution. TBH, that’s also the case for the R solution.

About the JavaScript code

The JavaScript code has been written in the same RMarkdown as the R code. It runs thanks to the {bubble} package: https://github.com/ColinFay/bubble

Instructions

Step 1

Inputs are of the form 1-3 a: abcde, for min-max letter:code, where letter must be found at least min and no more than max in code

How to: split the input in four columns, for min,max,letter, and code, count the number of letter in code, and then make sure this count is >= min and <= max.

Step 2

Inputs are of the form 1-3 a: abcde, for position1-position2 letter:code, where code[position1] == letter | code[position2] == letter but not code[position1] == letter & code[position2] == letter, nor !code[position1] == letter & !code[position2] == letter

Find the complete instructions at: https://adventofcode.com/2020/day/2.

R solution

Part one

# Read
ipt <- read.delim( "2020-02-aoc.txt",  header = FALSE )

library(dplyr, warn.conflicts = FALSE)
library(tidyr)
library(purrr)

ipt %>%
  # Create the four columns
  separate(V1, c("min", "max", "letter", "code")) %>%
  pmap_dbl(~{
    # If the letter is not in the input, return 0
    if (!stringr::str_detect(..4, ..3)) return(0)
    # Count the n of letter in code
    count <- stringr::str_count(..4, ..3)
    # Is this count between the boundaries?
    count >= as.numeric(..1) & count <= as.numeric(..2)
  }) %>% sum()

## [1] 607

Part two

ipt %>%
  # Create the four columns
  separate(V1, c("min", "max", "letter", "code")) %>%
  pmap_dbl(~{
    #browser()
    # Split the code
    code <- strsplit(..4, "")[[1]]
    # code[position1] == letter
    p1_match <- code[as.numeric(..1)] == ..3
    # code[position1] == letter
    p2_match <- code[as.numeric(..2)] == ..3
    # No match
    if (!p1_match & !p2_match) return(0)
    # Two matches
    if (p1_match && p2_match) return(0)
    return(1)
  }) %>% sum()

## [1] 321

JS solution

Part one & Two

// Reading the file and converting it to int

const fs = require('fs')
var ipt = fs.readFileSync("2020-02-aoc.txt", 'utf8').split("\n").filter(x => x.length != 0);
ipt = ipt.map(x => x.split(/[^A-Za-z0-9]/));

// Doing the combn

var res1 = ipt.map(x => {
  if (!x[4].includes(x[2])) return 0
  var match = x[4].match(new RegExp(x[2], "g")).length
  return match >= parseInt(x[0]) & match <= parseInt(x[1])
})

// Solution

// https://developer.mozilla.org/fr/docs/Web/JavaScript/Reference/Objets_globaux/Array/reduce
const reducer = (accumulator, currentValue) => accumulator + currentValue;
res1.reduce(reducer)

## undefined
## undefined
## 607

// Part 2

var res2 = ipt.map(x => {
    // Split the code
    var code = x[4].split("")
    // code[position1] == letter
    var p1_match = code[parseInt(x[0]) - 1] === x[2]
    // code[position1] == letter
    var p2_match = code[parseInt(x[1]) - 1] === x[2]
    // No match
    if (!p1_match && !p2_match) return 0
    // Two matches
    if (p1_match && p2_match) return 0
    return 1
})