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Advent of code - Day 4

qmenoret profile image Quentin Ménoret Updated on ・2 min read

Are you participating in the Advent of code this year?

If you don't know what the advent of code is, it's a website where you'll find a daily challenge (every day it gets harder). It's a really fun event, you should participate!

I try to solve the exercises using either JavaScript or TypeScript and will share my solutions daily (with one day delay so no one can cheat!). I only share the solution for the second part.

For day #4 I actually created 2 different solution. The first one was using a lot of different Regex:

input
  .split(/\r?\n\r?\n/)
  .filter((passport) => /byr:(19[2-9][0-9]|200[0-2])(\s|$)/.test(passport))
  .filter((passport) => /iyr:(201[0-9]|2020)(\s|$)/.test(passport))
  .filter((passport) => /eyr:(202[0-9]|2030)(\s|$)/.test(passport))
  .filter((passport) =>
    /hgt:((1[5-8][0-9]|19[0-3])cm)|(59|6[0-9]|7[0-6])in/.test(passport)
  )
  .filter((passport) => /hcl:\#[0-9a-f]{6}(\s|$)/.test(passport))
  .filter((passport) =>
    /ecl:(amb|blu|brn|gry|grn|hzl|oth)(\s|$)/.test(passport)
  )
  .filter((passport) => /pid:\d{9}(\s|$)/.test(passport));
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But As you can see, every filter contains a Regex... So I took the time to have some fun and group them into one. Don't try this at home!

const rg = /(?=(.|\n)*byr:(19[2-9][0-9]|200[0-2])(\s|$))(?=(.|\n)*iyr:(201[0-9]|2020)(\s|$))(?=(.|\n)*eyr:(202[0-9]|2030)(\s|$))(?=(.|\n)*hcl:\#([0-9a-f]{6})(\s|$))(?=(.|\n)*ecl:(amb|blu|brn|gry|grn|hzl|oth)(\s|$))(?=(.|\n)*pid:(\d{9})(\s|$))(?=(.|\n)*(hgt:((1[5-8][0-9]|19[0-3])cm)|(59|6[0-9]|7[0-6])in))/;

const result = input.split(/\r?\n\r?\n/).filter((passport) => rg.test(passport));
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But since there are some people even crazier than me, someone from my team adapted this code so it doesn't require any preprocessing (no need to split the string anymore!).

Here is the solution, with only a Regex:

const monster = /(?=(?:.|[^\n]\n)*byr:(?:19[2-9][0-9]|200[012])(?:\s|$))(?=(?:.|[^\n]\n)*iyr:20(?:1[0-9]|20)(?:\s|$))(?=(?:.|[^\n]\n)*eyr:20(?:2[0-9]|30)(?:\s|$))(?=(?:.|[^\n]\n)*hgt:(?:(?:59|6[0-9]|7[0-6])in|1(?:(?:[5-8][0-9]|9[0-3])cm))(?:\s|$))(?=(?:.|[^\n]\n)*hcl:#[0-9a-f]{6}(?:\s|$))(?=(?:.|[^\n]\n)*ecl:(?:amb|blu|brn|gry|grn|hzl|oth)(?:\s|$))(?=(?:.|[^\n]\n)*pid:[0-9]{9}(?:\s|$))([\w\W]+?)(?:\n\n|$)/g;

const result = input.match(monster).length;
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Feel free to share yours in the comments!


Photo by Markus Spiske on Unsplash

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