Ryan Palo

Posted on Dec 4, 2020 • Updated on Dec 12, 2020

Advent of Code 2020 Solution Megathread - Day 4: Passport Processing

#adventofcode #challenge

Day 4! I was worried as I was reading the first problem yesterday that I would have to optimize for any rational slope. I'm thankful he decided to take it easier than that for Day 3.

The Puzzle

In today’s puzzle, we're just trying to get through airport security, which is jam-packed because, obviously, Santa's magic keeps the North Pole COVID-free. It's classified as a hum-bug. 🥁 Anyways. The passport scanner is broken and we're doing a good deed by "fixing" it. And by "fixing," we mean "hacking it to let us through but also mostly fixing it."

Y'all. We are THIS close to validating YAML and I am here for it.

The Leaderboards

As always, this is the spot where I’ll plug any leaderboard codes shared from the community.

Ryan's Leaderboard: 224198-25048a19

If you want to generate your own leaderboard and signal boost it a little bit, send it to me either in a DEV message or in a comment on one of these posts and I'll add it to the list above.

Yesterday’s Languages

Updated 03:06PM 12/12/2020 PST.

Language	Count
Python	8
JavaScript	3
Rust	2
Haskell	2
C#	1
Raku	1
COBOL	1
PHP	1
Ruby	1
Elixir	1
Go	1
C	1

Merry Coding!

Top comments (23)

Benjamin Trent • Dec 4 '20

My super gross rust impl. Messy regex. I am sure there are way better ways to parse according to white space.

Also, I sort of went half-way with a struct solution. Probably would have been better to either go all the way or not have custom types at all.

#[derive(Debug)]
struct Passport {
    birth_year: Option<usize>,
    issue_year: Option<usize>,
    exp_year: Option<usize>,
    height: Option<String>,
    hair_color: Option<String>,
    eye_color: Option<String>,
    pid: Option<String>,
    cid: Option<usize>,
}

impl From<&str> for Passport {
    fn from(s: &str) -> Self {
        let (
            mut birth_year,
            mut issue_year,
            mut exp_year,
            mut height,
            mut hair_color,
            mut eye_color,
            mut pid,
            mut cid,
        ) = (
            Option::None,
            Option::None,
            Option::None,
            Option::None,
            Option::None,
            Option::None,
            Option::None,
            Option::None,
        );
        s.split(" ").filter(|i| !i.is_empty()).for_each(|i| {
            let name_var: Vec<&str> = i.split(":").collect();
            match name_var[0] {
                "byr" => birth_year = Option::Some(name_var[1].parse().unwrap()),
                "iyr" => issue_year = Option::Some(name_var[1].parse().unwrap()),
                "eyr" => exp_year = Option::Some(name_var[1].parse().unwrap()),
                "hgt" => height = Option::Some(String::from(name_var[1])),
                "hcl" => hair_color = Option::Some(String::from(name_var[1])),
                "ecl" => eye_color = Option::Some(String::from(name_var[1])),
                "pid" => pid = Option::Some(String::from(name_var[1])),
                "cid" => cid = Option::Some(name_var[1].parse().unwrap()),
                _ => {}
            }
        });
        Passport {
            birth_year,
            issue_year,
            exp_year,
            height,
            hair_color,
            eye_color,
            pid,
            cid,
        }
    }
}

impl Passport {
    pub fn is_valid(&self) -> bool {
        self.birth_year.is_some()
            && self.issue_year.is_some()
            && self.exp_year.is_some()
            && self.height.is_some()
            && self.hair_color.is_some()
            && self.eye_color.is_some()
            && self.pid.is_some()
    }

    pub fn is_valid_strict(&self) -> bool {
        self.valid_birth_year()
            && self.valid_issue_year()
            && self.valid_exp_year()
            && self.valid_hgt()
            && self.valid_hair()
            && self.valid_eyes()
            && self.valid_pid()
    }

    fn valid_birth_year(&self) -> bool {
        (1920..=2002).contains(&self.birth_year.unwrap_or_default())
    }

    fn valid_issue_year(&self) -> bool {
        (2010..=2020).contains(&self.issue_year.unwrap_or_default())
    }

    fn valid_exp_year(&self) -> bool {
        (2020..=2030).contains(&self.exp_year.unwrap_or_default())
    }

    fn valid_hgt(&self) -> bool {
        if let Some(height) = self.height.as_ref() {
            let range = match &height[height.len() - 2..] {
                "in" => (59..=76),
                "cm" => (150..=193),
                _ => return false,
            };
            range.contains(&height[0..height.len() - 2].parse::<usize>().unwrap_or(0))
        } else {
            false
        }
    }

    fn valid_hair(&self) -> bool {
        Passport::valid_str(self.hair_color.as_ref(), r"^#[0-9a-f]{6}$")
    }

    fn valid_eyes(&self) -> bool {
        Passport::valid_str(self.eye_color.as_ref(), r"^amb|blu|brn|gry|grn|hzl|oth$")
    }

    fn valid_pid(&self) -> bool {
        Passport::valid_str(self.pid.as_ref(), r"^[0-9]{9}$")
    }

    fn valid_str(maybe_str: Option<&String>, re: &str) -> bool {
        if let Some(str) = maybe_str {
            let re = regex::Regex::new(re).unwrap();
            let captures = re.captures(str.as_str());
            captures.is_some()
        } else {
            false
        }
    }
}

#[aoc_generator(day4)]
fn input_to_vec(input: &str) -> Vec<Passport> {
    let mut cleaned_str = String::from("");
    let mut cleaned_input: Vec<Passport> = vec![];
    input.lines().for_each(|i| {
        if i.is_empty() && !cleaned_str.is_empty() {
            cleaned_input.push(Passport::from(cleaned_str.as_str()));
            cleaned_str = String::from("");
        }
        cleaned_str += i;
        cleaned_str += " ";
    });
    if !cleaned_str.is_empty() {
        cleaned_input.push(Passport::from(cleaned_str.as_str()));
    }
    cleaned_input
}

#[aoc(day4, part1)]
fn valid_count(input: &Vec<Passport>) -> usize {
    input.iter().filter(|p| p.is_valid()).count()
}

#[aoc(day4, part2)]
fn strict_valid_count(input: &Vec<Passport>) -> usize {
    input.iter().filter(|p| p.is_valid_strict()).count()
}

Christopher Kruse • Dec 4 '20

You're not alone in the ugly feeling. I had a particularly nasty bug that gave me one result too many in part two (realized I had a missing ^ and $ on the regex for pid).

I see a fair amount of similarities in approach, so I'm glad to see I'm in good company. :D

As always, on Github.

use aoc_runner_derive::{aoc, aoc_generator};
use regex::Regex;

#[derive(Debug, PartialEq)]
struct Height {
    measure: usize,
    unit: String,
}

impl Height {
    fn parse(hgt_str: &str) -> Option<Height> {
        let re = Regex::new("(\\d+)(in|cm)").expect("Unable to create Regex");
        match re.captures(hgt_str) {
            None => None,
            Some(captures) => {
                let h = Height {
                    measure: str::parse(captures.get(1).unwrap().as_str())
                        .expect("Unable to parse number"),
                    unit: String::from(captures.get(2).unwrap().as_str()),
                };
                Some(h)
            }
        }
    }
    fn is_valid(&self) -> bool {
        match self.unit.as_str() {
            "cm" => self.measure >= 150 && self.measure <= 193,
            "in" => self.measure >= 59 && self.measure <= 76,
            _ => panic!("Not a valid unit"),
        }
    }
}

#[derive(Debug, PartialEq)]
struct Passport {
    byr: Option<usize>,
    iyr: Option<usize>,
    eyr: Option<usize>,
    hgt: Option<Height>,
    hgt_str: Option<String>,
    hcl: Option<String>,
    ecl: Option<String>,
    pid: Option<String>,
    cid: Option<String>,
}

impl Passport {
    fn new() -> Passport {
        Passport {
            byr: None,
            iyr: None,
            eyr: None,
            hgt: None,
            hgt_str: None,
            hcl: None,
            ecl: None,
            pid: None,
            cid: None,
        }
    }

    fn has_fields(&self) -> bool {
        self.byr.is_some()
            && self.iyr.is_some()
            && self.eyr.is_some()
            && self.hgt_str.is_some()
            && self.hcl.is_some()
            && self.ecl.is_some()
            && self.pid.is_some()
    }

    fn is_valid(&self) -> bool {
        self.valid_byr()
            && self.valid_iyr()
            && self.valid_eyr()
            && self.valid_hgt()
            && self.valid_hcl()
            && self.valid_ecl()
            && self.valid_pid()
    }

    fn valid_byr(&self) -> bool {
        match self.byr {
            None => false,
            Some(n) => n >= 1920 && n <= 2002,
        }
    }
    fn valid_iyr(&self) -> bool {
        match self.iyr {
            None => false,
            Some(n) => n >= 2010 && n <= 2020,
        }
    }
    fn valid_eyr(&self) -> bool {
        match self.eyr {
            None => false,
            Some(n) => n >= 2020 && n <= 2030,
        }
    }
    fn valid_hgt(&self) -> bool {
        match &self.hgt {
            None => false,
            Some(h) => h.is_valid(),
        }
    }
    fn valid_hcl(&self) -> bool {
        let re = Regex::new("^#[0-9a-f]{6}$").expect("Failed to make regex");
        match &self.hcl {
            None => false,
            Some(hair) => re.is_match(hair.as_str()),
        }
    }
    fn valid_ecl(&self) -> bool {
        let valid_colors = vec!["amb", "blu", "brn", "gry", "grn", "hzl", "oth"];
        match &self.ecl {
            None => false,
            Some(c) => valid_colors.contains(&c.as_str()),
        }
    }
    fn valid_pid(&self) -> bool {
        let re = Regex::new("^[0-9]{9}$").expect("Failed to build Regex");
        match &self.pid {
            None => false,
            Some(pid) => re.is_match(pid.as_str()),
        }
    }
}

#[aoc_generator(day4)]
fn parse_input_day4(input: &str) -> Vec<Passport> {
    input
        .split("\n\n")
        .map(|passport_str| parse_passport(passport_str))
        .collect()
}

fn parse_passport(passport_str: &str) -> Passport {
    let kv: Vec<&str> = passport_str
        .lines()
        .flat_map(|line| line.split(" "))
        .collect();
    let mut pass = Passport::new();
    for key_val in kv {
        let pair: Vec<&str> = key_val.split(":").collect();
        match *(pair.get(0).unwrap()) {
            "cid" => pass.cid = Some(String::from(*pair.get(1).unwrap())),
            "byr" => pass.byr = Some(str::parse(*pair.get(1).unwrap()).unwrap()),
            "iyr" => pass.iyr = Some(str::parse(*pair.get(1).unwrap()).unwrap()),
            "eyr" => pass.eyr = Some(str::parse(*pair.get(1).unwrap()).unwrap()),
            "hgt" => {
                pass.hgt_str = Some(str::parse(*pair.get(1).unwrap()).unwrap());
                pass.hgt = Height::parse(*pair.get(1).unwrap());
            }
            "hcl" => pass.hcl = Some(String::from(*pair.get(1).unwrap())),
            "ecl" => pass.ecl = Some(String::from(*pair.get(1).unwrap())),
            "pid" => pass.pid = Some(String::from(*pair.get(1).unwrap())),
            _ => panic!("Found passport code that doesn't match"),
        }
    }
    pass
}

#[aoc(day4, part1)]
fn count_valid_passports(input: &Vec<Passport>) -> usize {
    input.iter().filter(|pass| pass.has_fields()).count()
}

#[aoc(day4, part2)]
fn count_valid_data_passports(input: &Vec<Passport>) -> usize {
    input.iter().filter(|pass| pass.is_valid()).count()
}

Ali Spittel • Dec 4 '20

I hate problems like this:

class Validator:
    def __init__(self, passport):
        self.passport = passport

    def check_field_count(self):
        return len(self.passport) == 8 or (len(self.passport) == 7 and 'cid' not in self.passport)

    def check_year(self, key, start, end):
        return len(self.passport[key]) == 4 and int(self.passport[key]) >= start and int(self.passport[key]) <= end

    def check_byr(self):
        return self.check_year('byr', 1920, 2002)

    def check_iyr(self):
        return self.check_year('iyr', 2010, 2020)

    def check_eyr(self):
        return self.check_year('eyr', 2020, 2030)

    def check_hcl(self):
        return self.passport['hcl'][0] == "#" and self.passport['hcl'][1:].isalnum()

    def check_ecl(self):
        return self.passport['ecl'] in ['amb', 'blu', 'brn', 'gry', 'grn', 'hzl', 'oth']

    def check_pid(self):
        return len(self.passport['pid']) == 9

    def check_hgt(self):
        if self.passport['hgt'][-2:] == "cm":
            return int(self.passport['hgt'][:-2]) >= 150 and int(self.passport['hgt'][:-2]) <= 193
        elif self.passport['hgt'][-2:] == "in":
            return int(self.passport['hgt'][:-2]) >= 59 and int(self.passport['hgt'][:-2]) <= 76

    def is_valid(self):
        return (self.check_field_count() and self.check_byr() and self.check_iyr() and self.check_eyr() 
            and self.check_hcl() and self.check_ecl() and self.check_pid() and self.check_hgt())


def get_passports(inp):
    passports = []
    passport = {}
    for line in inp:
        if line != "\n":
            line = line.rstrip().split(" ")
            line = [field.split(":") for field in line]
            for field in line:
                passport[field[0]] = field[1]
        else:
            passports.append(passport)
            passport = {}
    passports.append(passport)
    return passports


with open('input.txt') as inp:
    passports = get_passports(inp)
    validators = [Validator(passport) for passport in passports]
    part_1_count = 0
    part_2_count = 0
    for validator in validators:
        if validator.check_field_count(): 
            part_1_count += 1
        if validator.is_valid(): 
            part_2_count += 1                        

    print(part_1_count) 
    print(part_2_count)

Grant Finneman • Dec 21 '20

Thank you so much for the clear and concise python, I'm new to python and thought this would be an excellent way to learn it. I figured this one out eventually and thought I would come here to see how someone else did it. I don't understand how yours doesn't throw a key error when trying to access dictionary keys that aren't there. I need to learn more about classes but I don't know why this works. If you could point me in the right direction I'd greatly appreciate it. Thank you again for the wonderful example

Yuan Gao • Dec 5 '20

I went ahead and wrote a solution using PEG in Python (parsimonious library). Aside from the slightly compact PEG grammar, the rest of it is very readable


from parsimonious.grammar import Grammar, NodeVisitor
from parsimonious.exceptions import ParseError, IncompleteParseError, VisitationError

grammar = Grammar(r"""
    EXPR  = ITEM+
    ITEM  = (BYR / IYR / EYR / HGT / HCL / ECL / PID / CID) WHITE?
    WHITE =  ~r"[\s]+"

    BYR   = "byr:" NUMB
    IYR   = "iyr:" NUMB
    EYR   = "eyr:" NUMB
    HGT   = "hgt:" (HGTCM / HGTIN)
    HCL   = "hcl:" ~r"#[0-9a-f]{6}"
    ECL   = "ecl:" ("amb" / "blu" / "brn" / "gry" / "grn" / "hzl" / "oth") 
    PID   = "pid:" ~r"[0-9]{9}"
    CID   = "cid:" ~r"[0-9a-zA-Z]*"

    HGTCM = NUMB "cm"
    HGTIN = NUMB "in"

    NUMB  = ~r"[0-9]{2,4}"
""")

class PassportVisitor(NodeVisitor):
    def visit_EXPR(self, node, visited_children):
        assert not {"BYR", "IYR", "EYR", "HGT", "HCL", "ECL", "PID"}.difference(visited_children)

    def visit_ITEM(self, node, visited_children):
        return node.children[0].children[0].expr_name

    def visit_BYR(self, node, visited_children):
        assert 1920 <= visited_children[1] <= 2002

    def visit_IYR(self, node, visited_children):
        assert 2010 <= visited_children[1] <= 2020

    def visit_EYR(self, node, visited_children):
        assert 2020 <= visited_children[1] <= 2030

    def visit_HGTCM(self, node, visited_children):
        assert 150 <= visited_children[0] <= 193

    def visit_HGTIN(self, node, visited_children):
        assert 59 <= visited_children[0] <= 76

    def visit_NUMB(self, node, visited_children):
        return int(node.text)

    def generic_visit(self, node, visited_children):
        return visited_children or node

pv = PassportVisitor()
pv.grammar = grammar

data = open("input.txt").read().split("\n\n")
valid = 0
for entry in data:
    try:
        pv.parse(entry)
    except (ParseError, VisitationError, IncompleteParseError):
        continue
    else:
        valid += 1
print("Valid:", valid)

Anna • Dec 4 '20

Not my finest work, I took advantage of the fact that some problems didn't arise in the test data. Then again, this isn't real life, it's a game and I got the stars. 😉

Part 2 here.

   IDENTIFICATION DIVISION.
   PROGRAM-ID. AOC-2020-04-1.
   AUTHOR. ANNA KOSIERADZKA.

   ENVIRONMENT DIVISION.
   INPUT-OUTPUT SECTION.
   FILE-CONTROL.
       SELECT INPUTFILE ASSIGN TO "d4.input"
       ORGANIZATION IS LINE SEQUENTIAL.

   DATA DIVISION.
   FILE SECTION.
     FD INPUTFILE
     RECORD IS VARYING IN SIZE FROM 1 to 99
     DEPENDING ON REC-LEN.
     01 INPUTRECORD PIC X(99).
   WORKING-STORAGE SECTION.
     01 FILE-STATUS PIC 9 VALUE 0.
     01 REC-LEN PIC 9(2) COMP.
     01 WS-ROW PIC X(16) OCCURS 8 TIMES.
     01 WS-CHAR PIC X.

   LOCAL-STORAGE SECTION.
     01 CORRECT-PASSPORTS UNSIGNED-INT VALUE 0.
     01 FOUND-FIELDS UNSIGNED-INT VALUE 0.
     01 STRING-PTR UNSIGNED-INT VALUE 1.
     01 I UNSIGNED-INT VALUE 1.

   PROCEDURE DIVISION.
   001-MAIN.
       OPEN INPUT INPUTFILE.
       PERFORM 002-READ UNTIL FILE-STATUS = 1.
       CLOSE INPUTFILE.
       PERFORM 004-NEXT-PASSPORT.
       DISPLAY CORRECT-PASSPORTS.
       STOP RUN.

   002-READ.
        READ INPUTFILE
            AT END MOVE 1 TO FILE-STATUS
            NOT AT END PERFORM 003-PROCESS-RECORD
        END-READ.

   003-PROCESS-RECORD.
       IF REC-LEN = 0 THEN
          PERFORM 004-NEXT-PASSPORT
       ELSE 
          PERFORM 005-PROCESS-ROW
       END-IF.

   004-NEXT-PASSPORT.
       IF FOUND-FIELDS = 7 THEN 
          ADD 1 TO CORRECT-PASSPORTS
       END-IF.
       MOVE 0 TO FOUND-FIELDS.

   005-PROCESS-ROW.
       MOVE 1 TO STRING-PTR.
       PERFORM VARYING I FROM 1 BY 1 UNTIL I > 8
         UNSTRING INPUTRECORD DELIMITED BY SPACE INTO WS-ROW(I)
         WITH POINTER STRING-PTR
       END-PERFORM.

       PERFORM VARYING I FROM 1 BY 1 UNTIL I > 8
          MOVE WS-ROW(I)(1:1) TO WS-CHAR
          IF NOT WS-CHAR ='c' AND NOT WS-CHAR = ' ' THEN
             ADD 1 TO FOUND-FIELDS
          END-IF
       END-PERFORM.

Derk-Jan Karrenbeld • Dec 5 '20 • Edited

I feel this reads as quite elegant in Ruby -- or at least my implementation of it.

Hoping on something more interesting to do for Day 5!

require 'benchmark'

class Passport
  RULES = {
    byr: -> (value) { /^[0-9]{4}$/.match?(value) && (1920..2002).cover?(value.to_i) },
    iyr: -> (value) { /^[0-9]{4}$/.match?(value) && (2010..2020).cover?(value.to_i) },
    eyr: -> (value) { /^[0-9]{4}$/.match?(value) && (2020..2030).cover?(value.to_i) },
    hgt: -> (value) {
      match = /(^[1-9][0-9]+)(cm|in)$/.match(value)

      match && (
        (match[2] == 'cm' && (150..193).cover?(match[1].to_i)) ||
        (match[2] == 'in' && (59..76).cover?(match[1].to_i))
      )
    },
    hcl: -> (value) { /^\#[0-9a-f]{6}$/.match? value },
    ecl: -> (value) { %w[amb blu brn gry grn hzl oth].include?(value) },
    pid: -> (value) { /^[0-9]{9}$/.match? value }
  }

  def self.from(lines)
    fields = lines.split(' ')

    new(fields.each_with_object({}) do |kv, results|
      k, v = kv.chomp.split(':')
      results[k.to_sym] = v
    end)
  end

  def initialize(fields)
    self.fields = fields
  end

  def [](field)
    fields[field]
  end

  def valid?
    RULES.keys.all? { |field| RULES[field].(self[field]) }
  end

  private

  attr_accessor :fields
end

data = File.read('input.txt')
passports = data
  .split(/\n\n/)
  .map do |l|
    Passport.from(l)
  end

Benchmark.bmbm do |b|
  b.report do
    puts passports.count(&:valid?)
  end
end

Erik Bäckman • Dec 16 '20 • Edited

Still not doing these the day the come out but here's my Haskell solution.
Problems like these seem like work to me :P

{-# LANGUAGE LambdaCase #-}
module Day4 where

import Text.Parsec
import Text.Parsec.String
import Control.Monad (guard)
import Data.Maybe (mapMaybe, isJust)
import Data.List.Split hiding (sepBy, endBy, oneOf)
import qualified Data.Map as M
import Data.Map (Map)
import Data.List ((\\))
import Text.Read (readMaybe)
import Data.Char
import Data.Semigroup (All(All), getAll)

hush :: Either e a -> Maybe a
hush (Left _)  = Nothing
hush (Right a) = Just a

parse' :: Parser a -> String -> Maybe a
parse' p = hush . parse p ""

-- Part 1
parsePassport :: String -> Either ParseError (Map String String)
parsePassport = fmap M.fromList . parse' (kvp `sepEndBy` space)
  where
    kvp = (,) <$> manyTill anyChar (char ':')
              <*> many (noneOf "\n ")

hasRequiredFields :: Map String String -> Bool
hasRequiredFields m =  null $ ["byr", "ecl", "eyr", "hcl", "hgt", "iyr", "pid"] \\ M.keys m

validatePassports :: (Map String String -> Bool) -> String -> [Map String String]
validatePassports v = filter v . mapMaybe (hush . parsePassport) . splitOn "\n\n"

solveP1 :: String -> Int
solveP1 = length . validatePassports hasRequiredFields

-- Part 2
type Validation a = (a -> Maybe a)

within :: (Int, Int) -> Int -> Bool
within (min, max) i = i >= min && i <= max

year :: String -> Maybe Int
year s = parse' (4 `times` digit) s >>= readMaybe

yearBetween :: (Int, Int) -> String -> Maybe String
yearBetween r s = year s >>= \n -> guard (within r n) >> pure s

byr :: Validation String
byr = yearBetween (1929, 2020)

iyr :: Validation String
iyr = yearBetween (2010, 2020)

eyr :: Validation String
eyr = yearBetween (2020, 2030)

hgt :: Validation String
hgt = parse' (mappend <$> many1 digit <*> (try (string "cm") <|> try (string "in")))

hcl :: Validation String
hcl = parse' (mappend <$> string "#" <*> 6 `times` anyChar)

ecl :: Validation String
ecl s | s == "amb" = Just s
      | s == "blu" = Just s
      | s == "brn" = Just s
      | s == "gry" = Just s
      | s == "grn" = Just s
      | s == "hzl" = Just s
      | s == "oth" = Just s
      | otherwise  = Nothing

pid :: Validation String
pid s = guard (length s == 9 && isNumber s) >> pure s
  where isNumber = getAll . foldMap (All . isDigit)

validateFields :: Map String String -> Maybe (Map String String)
validateFields = M.traverseWithKey validateAtKey
  where
    validateAtKey = \case "byr" -> byr
                          "iyr" -> iyr
                          "eyr" -> eyr
                          "hgt" -> hgt
                          "hcl" -> hcl
                          "ecl" -> ecl
                          _     -> Just

solveP2 :: String -> Int
solveP2 = length . validatePassports (\x -> hasRequiredFields x &&
                                            isJust (validateFields x))

Phantz • Dec 5 '20 • Edited

would anyone be interested in a solution written entirely in C, without regex or hashtables

static char const* formats[] = {
    " byr:19%*2[0-9]%n", " byr:200%*1[0-2]%n",
    " iyr:201%*1[0-9]%n", " iyr:2020%n",
    " eyr:202%*1[0-9]%n", " eyr:2030%n",
    " hgt:1%*1[5-8]%*1[0-9]cm%n", " hgt:19%*1[0-3]cm%n",
        " hgt:59in%n", " hgt:6%*1[0-9]in%n", " hgt:7%*1[0-6]in%n",
    " hcl:#%*x%n",
    " ecl:amb%n", " ecl:blu%n", " ecl:brn%n", " ecl:gr%*1[yn]%n", " ecl:hzl%n", " ecl:oth%n",
    " pid:%*9[0-9]%n",
    " cid:%*s%n"
};

static bool is_valid(char const* s)
{
    size_t count = 0;
    for (int n = 0, prevn = -1; n != prevn && s[n] != '\0';)
    {
        prevn = n;
        for (size_t i = 0; i < sizeof formats / sizeof * formats; i++)
        {
            int _n = 0;
            sscanf(s + n, formats[i], &_n);
            if (_n != 0)
            {
                n += _n;
                count += 1;
                formats[i] = "";
                break;
            }
        }
    }
    return count >= 7;
}

The input s to is_valid should be a full passport string (what you get after splitting by double new lines). It does parsing + validation at once and eagerly exits if any field validation fails.

Yes, I know - very cursed. 'twas just for fun, and to prove a point ;)

Stefan Linke • Dec 5 '20

Warning this might be offensive to some :D
My Saturday was too long, so I created a code-golfed PHP version (for both parts)

<?$r=['byr):((19[2-9]\d|200[0-2]','iyr):((201\d|2020','eyr):((202\d|2030','hgt):(((?:1[5-8]\d|19[0-3])cm|(?:59|6\d|7[0-6])in','hcl):((#[\da-f]{6}','ecl):((amb|blu|brn|gry|grn|hzl|oth','pid):((\d{9}'];foreach(explode("

",file_get_contents('input'))as$p){$s=$t=1;for($i=0;$i<7;)if(!preg_match("/(?:^|\s)({$r[$i++]})(\s|$))?/",$p,$m))$s=$t=0;elseif(!($m[2]??0))$t=0;$x+=$s;$y+=$t;}echo"$x $y";

Stefan Linke • Dec 5 '20

Go again, a bit hacky with the very last element

package main

import (
    "bufio"
    "fmt"
    "io"
    "os"
    "regexp"
    "strconv"
    "strings"
)

var requiredAttributes = []string{"byr", "iyr", "eyr", "hgt", "hcl", "ecl", "pid"}

func isValid(passport map[string]string) bool {
    for _, attribute := range requiredAttributes {
        if _, exists := passport[attribute]; !exists {
            return false
        }
    }

    return true
}

func exists(slice []string, val string) bool {
    for _, item := range slice {
        if item == val {
            return true
        }
    }
    return false
}

func validateRange(val string, lower, upper int) bool {
    num, err := strconv.Atoi(val)
    return err == nil && num >= lower && num <= upper
}

func isValidV2(passport map[string]string) bool {
    for attr, val := range passport {
        switch attr {
        case "byr":
            if !validateRange(val, 1920, 2002) {
                return false
            }
        case "iyr":
            if !validateRange(val, 2010, 2020) {
                return false
            }
        case "eyr":
            if !validateRange(val, 2020, 2030) {
                return false
            }

        case "hgt":
            if strings.HasSuffix(val, "cm") {
                if !validateRange(strings.TrimSuffix(val, "cm"), 150, 193) {
                    return false
                }
            } else if strings.HasSuffix(val, "in") {
                if !validateRange(strings.TrimSuffix(val, "in"), 59, 76) {
                    return false
                }
            } else {
                return false
            }

        case "hcl":
            if match, _ := regexp.MatchString("^#[0-9a-f]{6}$", val); !match {
                return false
            }

        case "ecl":
            eyeColors := []string{"amb", "blu", "brn", "gry", "grn", "hzl", "oth"}
            if !exists(eyeColors, val) {
                return false
            }

        case "pid":
            if match, _ := regexp.MatchString("^[0-9]{9}$", val); !match {
                return false
            }
        }
    }

    return true
}

func main() {
    reader := bufio.NewReader(os.Stdin)
    passport := make(map[string]string, 8)

    numValid, numValidV2 := 0, 0
    for {
        var line string
        line, err := reader.ReadString('\n')
        if err == io.EOF {
            break
        }

        line = strings.TrimSpace(line)

        if len(line) == 0 {
            // passport complete
            if isValid(passport) {
                numValid++
                if isValidV2(passport) {
                    numValidV2++
                }
            }
            // reset passport
            passport = make(map[string]string, 8)
        } else {
            parts := strings.Split(line, " ")
            for _, part := range parts {
                attribute := strings.Split(part, ":")
                passport[attribute[0]] = attribute[1]
            }
        }
    }

    // last one is special snowflake, as file does not end with 2 newlines
    if isValid(passport) {
        numValid++
        if isValidV2(passport) {
            numValidV2++
        }
    }

    fmt.Println(numValid, numValidV2)
}

Seth Etter • Dec 5 '20

Feels like it could have been cleaner, my first round was worse though! I refactored to use Result and the ? error propagation operator, which was fun.

use regex::Regex;
use anyhow::{anyhow, Result};

#[derive(Clone)]
struct Passport {
    byr: Option<String>,
    iyr: Option<String>,
    eyr: Option<String>,
    hgt: Option<String>,
    hcl: Option<String>,
    ecl: Option<String>,
    pid: Option<String>,
    cid: Option<String>,
}

impl Default for Passport {
    fn default() -> Self {
        Passport {
            byr: None, iyr: None, eyr: None, hgt: None,
            hcl: None, ecl: None, pid: None, cid: None,
        }
    }
}

fn main() {
    let input = std::fs::read_to_string("input.txt").unwrap();

    let passports: Vec<Passport> = input.trim().split("\n\n").map(parse_passport).collect();
    let num_valid = passports.into_iter().filter(|p| {
        // validate_passport(p).is_ok()
        match validate_passport(p) {
            Ok(_) => true,
            Err(e) => { println!("{}", e); false },
        }
    }).count();

    println!("Num Valid: {}", num_valid);
}

fn parse_passport(input: &str) -> Passport {
    let mut p: Passport = Passport::default();
    for entry in input.replace("\n", " ").split(" ") {
        let parts: Vec<&str> = entry.split(":").collect();
        let (label, value) = (parts[0], parts[1]);
        match label {
            "byr" => { p.byr = Some(value.to_owned()) },
            "iyr" => { p.iyr = Some(value.to_owned()) },
            "eyr" => { p.eyr = Some(value.to_owned()) },
            "hgt" => { p.hgt = Some(value.to_owned()) },
            "hcl" => { p.hcl = Some(value.to_owned()) },
            "ecl" => { p.ecl = Some(value.to_owned()) },
            "pid" => { p.pid = Some(value.to_owned()) },
            "cid" => { p.cid = Some(value.to_owned()) },
            _ => {},
        }
    }
    p
}

fn validate_passport(p: &Passport) -> Result<()> {
    check_year_range(p.clone().byr, 1920, 2002)?;
    check_year_range(p.clone().iyr, 2010, 2020)?;
    check_year_range(p.clone().eyr, 2020, 2030)?;
    check_height(p.clone().hgt)?;
    check_regex(p.clone().hcl, "#[0-9A-Fa-f]{6}")?;
    check_regex(p.clone().ecl, "^(amb|blu|brn|gry|grn|hzl|oth)$")?;
    check_regex(p.clone().pid, "^[0-9]{9}$")?;
    Ok(())
}

fn check_year_range(year_str: Option<String>, min: usize, max: usize) -> Result<()> {
    let year = year_str.ok_or(anyhow!("Missing value"))?.parse::<usize>()
        .map_err(|_e| anyhow!("Failed to parse year_str"))?;
    if year < min || year > max {
        return Err(anyhow!("Year out of range"));
    }
    Ok(())
}

fn check_height(height: Option<String>) -> Result<()> {
    let hgt = height.ok_or(anyhow!("Missing hgt"))?;

    let re = Regex::new(r"^([0-9]+)(cm|in)$").unwrap();
    let caps = re.captures(hgt.as_str()).ok_or(anyhow!("Invalid height format"))?;

    let num_str = caps.get(1).unwrap().as_str();
    let unit = caps.get(2).unwrap();

    let num = num_str.parse::<usize>().map_err(|_e| anyhow!("Failed to parse height value"))?;

    match unit.as_str() {
        "in" if num < 59 || num > 76 => { return Err(anyhow!("Height out of range")); },
        "cm" if num < 150 || num > 193 => { return Err(anyhow!("Height out of range")); },
        _ => {},
    }
    Ok(())
}

fn check_regex(field: Option<String>, re_str: &str) -> Result<()> {
    let re = Regex::new(re_str).unwrap();
    let val = field.ok_or(anyhow!("Field missing"))?;
    match re.is_match(val.as_str()) {
        true => Ok(()),
        false => Err(anyhow!(format!("Regex mismatch: {}, {}", re_str, val))),
    }
}

Mustafa Haddara • Dec 5 '20

Reading all of these solutions, I'm glad I opted to avoid regexes in my answers! There are some messy hacks here ("1234567890abcdef".indexOf(c) stands out) and the types should probably all have been string? instead of string, which would have made this a little more concise, but I'm still pretty happy with how it turned out.

I am annoyed they decided to put multiple K:V pairs on the same line because it made the parsing a little messier but oh well.

import { SolveFunc } from './types';

export const solve: SolveFunc = (lines: string[]) => {
  const passports: Passport[] = parse_passports(lines);
  return passports.filter((p) => is_valid(p)).length.toString();
};

type Passport = {
  byr: string;
  iyr: string;
  eyr: string;
  hgt: string;
  hcl: string;
  ecl: string;
  pid: string;
  cid: string;
};

const parse_passports = (lines: string[]): Passport[] => {
  let p: Passport = make_blank_passport();
  const result = [p];
  for (let i = 0; i < lines.length; i++) {
    const line = lines[i];
    if (line.trim() === '') {
      p = make_blank_passport();
      result.push(p);
    }
    line.split(' ').map((chunk) => {
      const [k, v] = chunk.split(':');
      p[k] = v;
    });
  }
  return result;
};

const make_blank_passport = (): Passport => {
  return {
    byr: null,
    iyr: null,
    eyr: null,
    hgt: null,
    hcl: null,
    ecl: null,
    pid: null,
    cid: null,
  };
};

const is_valid = (p: Passport): boolean => {
  return (
    check_int(p.byr, 1920, 2002) &&
    check_int(p.iyr, 2010, 2020) &&
    check_int(p.eyr, 2020, 2030) &&
    check_height(p.hgt) &&
    check_hair_color(p.hcl) &&
    check_eye_color(p.ecl) &&
    check_passport_id(p.pid)
  );
};

const check_int = (strval, min, max) => {
  if (!strval) return false;
  const val = parseInt(strval);
  return min <= val && val <= max;
};

const check_height = (strval) => {
  if (!strval) return false;
  if (strval.endsWith('cm')) {
    const [h] = strval.split('cm');
    return check_int(h, 150, 193);
  } else if (strval.endsWith('in')) {
    const [h] = strval.split('in');
    return check_int(h, 59, 76);
  }
  return false;
};

const check_hair_color = (strval) => {
  if (!strval) return false;
  if (strval.startsWith('#') && strval.length === 7) {
    return strval.split('').filter((c) => '1234567890abcdef'.indexOf(c) < 0).length === 1;
  }
  return false;
};

const check_eye_color = (strval) => {
  if (!strval) return false;
  const accepted = ['amb', 'blu', 'brn', 'gry', 'grn', 'hzl', 'oth'];
  return accepted.indexOf(strval) >= 0;
};

const check_passport_id = (strval) => {
  if (!strval) return false;
  if (strval.length !== 9) return false;
  strval.split('').map((c) => parseInt(c));
  return true;
};

Kudos Beluga • Dec 4 '20 • Edited

I might have created the dirtiest js code in the world for this

let fs = require("fs"),part2 = true, fields = ['iyr','ecl','byr','hcl','eyr','hgt','pid'],pass = 0;
fs.readFile("input.txt","utf8",(err,data) => {
  if (err) throw err;
data.split(/\n\s/gi).map(e => {
  let isvalid = true;
 for (i in fields) {
   let match = e.match(new RegExp(`(?<=${fields[i]}:)[A-Z#a-z0-9]+`,"g"))
  if (!match) isvalid=false; else if (part2) {
      match = match[0];
     switch (fields[i]) {   
        case "byr":
        if (!(Number(match)>= 1920 && Number(match)<= 2002)) isvalid=false;
        break;
        case "iyr":
        if (!(Number(match)>= 2010 && Number(match)<= 2020)) isvalid=false;
        break;
        case "eyr":
        if (!(Number(match)>= 2020 && Number(match)<= 2030)) isvalid=false;
        break;
        case "hgt":
        if (match.slice(match.length-2,match.length) == "cm") {
          if (!(Number(match.split("").splice(0,match.length-2).join("")) >= 150 && Number(match.split("").splice(0,match.length-2).join("")) <= 193)) isvalid = false;
         } else {
          if (!(Number(match.split("").splice(0,match.length-2).join("")) >= 59 && Number(match.split("").splice(0,match.length-2).join("")) <= 76)) isvalid = false;
        }
        break;
        case "hcl":
          if (!(match.match(/#([a-f0-9]){6}/i))) isvalid = false;
        break;
        case "ecl":
        let haircolor = ["amb","blu","brn","gry","grn","hzl","oth"].map(e => {
          if (match == e) return "valid"
          }).filter(e => e)
        if (!haircolor.length) isvalid = false;
        break;
        case "pid":
        if(!(match.length == 9)) isvalid = false;
        break;
     }}} if (isvalid) pass++}); console.log(pass) })

willsmart • Dec 4 '20 • Edited

Plain forgot to break out of the comfort zone and use something other than javascript :|
I'll try C tomorrow

Here's today:

const input = require('fs')
  .readFileSync('4.txt', 'utf-8')
  .split(/\n{2,}/g)
  .map(s => Object.fromEntries(s.split(/\s+/g).map(s => s.split(':'))));

console.log({
  input: input.map(v => ({ v: JSON.stringify(v), isValid: isValid(v), check: check(v) })),
  count: input.reduce((acc, v) => acc + isValid(v), 0),
});

function check(v) {
  return ['byr', 'iyr', 'eyr', 'hgt', 'hcl', 'ecl', 'pid']
    .flatMap(k => (k in v && !validPair(k, v[k]) ? k : []))
    .join(' ');
}
function isValid(v) {
  return ['byr', 'iyr', 'eyr', 'hgt', 'hcl', 'ecl', 'pid'].reduce(
    (acc, k) => acc && k in v && validPair(k, v[k]),
    true
  );
}

function validPair(k, v) {
  let m;
  switch (k) {
    case 'byr':
      return v.length === 4 && v >= 1920 && v <= 2002;
    case 'iyr':
      return v.length === 4 && v >= 2010 && v <= 2020;
    case 'eyr':
      return v.length === 4 && v >= 2020 && v <= 2030;
    case 'hgt':
      if ((m = /^([\d.]+)cm$/.exec(v))) return m[1] >= 150 && m[1] <= 193;
      if ((m = /^([\d.]+)in$/.exec(v))) return m[1] >= 59 && m[1] <= 76;
      return false;
    case 'hcl':
      return /^#[0-9a-f]{6}$/.test(v);
    case 'ecl':
      return ['amb', 'blu', 'brn', 'gry', 'grn', 'hzl', 'oth'].includes(v);
    case 'pid':
      return /^[0-9]{9}$/.test(v);
  }
}

(added check as a way to see which field validator was broken when I failed part 2 the first time. It was a stupid typo in 'ecl')

Ryan Palo • Dec 4 '20

This was a long one, but I learned a ton about the <string.h> library. I also incremented a macro by 1 and spent 3 hours chasing a segfault. So, all in all, I think it sounds like we all had similar days. There are also several edge cases that I'm pretty sure my code doesn't cover, BUT that doesn't matter because this is AoC and it's not wrong if you get the stars. Right? Right?

Day4.h:

#ifndef AOC2020_DAY4_H
#define AOC2020_DAY4_H

/// Day 4: Passport Processing
///
/// Pick through passports made up of key/value pairs to figure out
/// which ones are valid.

#include <stdlib.h>
#include <stdbool.h>

#define NUM_PASS_FIELDS 8  ///< Number of fields in a SimplePassport
#define MAX_ENTRY_SIZE 20  ///< Max size of possible value in key/value
#define KEY_SIZE 4         ///< Size of a key in key/value
#define HAIR_COLOR_SIZE 8  ///< Size of a well-formed hair color
#define PID_SIZE 10        ///< Size of a well-formed PID

/// A simple passport just has certain fields or not.  Valid ones have
/// them all, with 'cid' being optional.
typedef struct {
  bool byr;
  bool iyr;
  bool eyr;
  bool hgt;
  bool hcl;
  bool ecl;
  bool pid;
  bool cid;
} SimplePassport;

/// Parses the input file, which is a series of passports.  Each key/val
/// is separated by a space or newline.  Passports are separated by 
/// two newlines.  Returns a list of passport structs.
SimplePassport* parse_simple_passports(const char* filename, int* count);

/// Counts the number of valid passports.  Passports are valid if
/// the have all keys, except CID is optional.
int part1(SimplePassport* passes, int count);

// ============== Part 2 ================== //

/// Possible values for height units: none, inches, or centimeters.
typedef enum {
  HT_BAD,
  HT_IN,
  HT_CM,
} HeightUnit;

/// A height is a measurement associated with a set of units.
typedef struct {
  int value;
  HeightUnit units;
} Height;

/// Possible options for eye color
typedef enum {
  EYE_BAD,
  EYE_AMBER,
  EYE_BLUE,
  EYE_BROWN,
  EYE_GREY,
  EYE_GREEN,
  EYE_HAZEL,
  EYE_OTHER,
} EyeColor;

/// A fancy passport has strict value validation for all fields.
/// Note: all fields here must be present to win.
typedef struct {
  /// Birth Year: 1920 <= x <= 2002
  int byr; 
  /// Issue Year: 2010 <= x <= 2020
  int iyr;
  /// Expiration Year: 2020 <= x <= 2030
  int eyr;
  /// Height: 150 <= cm <= 193 || 59 <= in <= 76
  Height hgt;
  /// Hair Color: # followed by 6 chars 0-9 or a-f
  char hcl[8];
  /// Eye Color: amb | blu | brn | gry | grn | hzl | oth
  EyeColor ecl;
  /// Passport ID : Exactly 9 digits.  (Storing 10 to find invalid ones)
  char pid[10];
} FancyPassport;

/// Parse fancy passports from an input file.  The number of them
/// is stored in 'count'.
FancyPassport* parse_fancy_passports(const char* filename, int* count);

/// Counts the number of valid fancy passports based on the rules above.
int part2(FancyPassport* passes, int count);

/// Runs both parts.
int day4(void);
#endif

Day4.c:

#include "Day4.h"

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

/// Loops through a file and counts all instances of double-newlines.
/// Adds one at the end for the last entry which doesn't have a trailing
/// double-newline.
static int count_passports(FILE* fp) {
  int count = 0;
  while (!feof(fp)) {
    if (getc(fp) == '\n' && getc(fp) == '\n') count++;
  }
  count++; // No double newline after last one.

  rewind(fp);
  return count;
}

/// Parses a single passport from a file.  Leaves the file pointer 
/// after the trailing double-newline, ready to parse the next one.
static SimplePassport parse_simple_passport(FILE* fp) {
  char key[4];
  char value[20];
  SimplePassport passport = {0};

  while (!feof(fp) && getc(fp) != '\n') {
    memset(key, 0, 4);
    memset(value, 0, 20);
    fseek(fp, -1, SEEK_CUR); // Un-eat the previous char because we need it.
    fgets(key, KEY_SIZE, fp);

    fscanf(fp, "%s", value);  // Eat the colon, value
    getc(fp);  // Eat white space?

    if (strcmp(key, "byr") == 0) passport.byr = true;
    else if (strcmp(key, "iyr") == 0) passport.iyr = true;
    else if (strcmp(key, "eyr") == 0) passport.eyr = true;
    else if (strcmp(key, "hgt") == 0) passport.hgt = true;
    else if (strcmp(key, "hcl") == 0) passport.hcl = true;
    else if (strcmp(key, "ecl") == 0) passport.ecl = true;
    else if (strcmp(key, "pid") == 0) passport.pid = true;
    else if (strcmp(key, "cid") == 0) passport.cid = true;
    else {
      printf("Unrecognized key: %s\n", key);
    }
  }
  return passport;
}

SimplePassport* parse_simple_passports(const char* filename, int* count) {
  FILE* fp;
  fp = fopen(filename, "r");
  if (fp == NULL) {
    printf("Couldn't open file.\n");
    exit(EXIT_FAILURE);
  }

  *count = count_passports(fp);
  SimplePassport* passes = (SimplePassport*)malloc(sizeof(SimplePassport) * *count);

  for (int i = 0; i < *count; i++) {
    passes[i] = parse_simple_passport(fp);
  }

  fclose(fp);
  return passes;
}

int part1(SimplePassport* passes, int count) {
  int invalid = 0;
  for (int i = 0; i < count; i++) {
    bool* p = (bool*)&passes[i];

    // Iterates over each field of the passport by using the bytes of
    // the struct as an array of bools.  Which should be OK?
    for (int j = 0; j < NUM_PASS_FIELDS - 1; j++) {
      if (p[j] == false) {
        invalid++;
        break;
      };
    }
  }
  return count - invalid;
}

// ================= Part 2 ===================== //

/// Parses a height string to a Height struct.  Well-formed strings
/// are [0-9]+(in|cm).  If it's invalid, leaves the value as 0 and
/// the units as HT_BAD.
static Height parse_height(char* value) {
  Height h;
  int possible_value;
  char units[4];
  sscanf(value, "%d%s", &possible_value, units);

  if (strcmp(units, "in") == 0) {
    h.value = possible_value;
    h.units = HT_IN;
  } else if (strcmp(units, "cm") == 0) {
    h.value = possible_value;
    h.units = HT_CM;
  } else {
    h.value = 0;
    h.units = HT_BAD;
  }
  return h;
}

/// Parses an EyeColor from a string.
static EyeColor parse_eye_color(char* value) {
  if (strcmp(value, "amb") == 0) return EYE_AMBER;
  if (strcmp(value, "blu") == 0) return EYE_BLUE;
  if (strcmp(value, "brn") == 0) return EYE_BROWN;
  if (strcmp(value, "gry") == 0) return EYE_GREY;
  if (strcmp(value, "grn") == 0) return EYE_GREEN;
  if (strcmp(value, "hzl") == 0) return EYE_HAZEL;
  if (strcmp(value, "oth") == 0) return EYE_OTHER;
  return EYE_BAD;
}

/// Prints out a FancyPassport for debugging.
static void print_fancy_passport(FancyPassport* p) {
  printf("Passport:\n");
  printf("BYR: %d\nIYR: %d\nEYR: %d\n", p->byr, p->iyr, p->eyr);
  printf("HGT: %d-%d\nHCL: %s\nECL: %d\n", p->hgt.value, p->hgt.units, p->hcl, p->ecl);
  printf("PID: %s\n", p->pid);
}

/// Parses a single fancy passport from a file.
static FancyPassport parse_fancy_passport(FILE* fp) {
  char key[KEY_SIZE];
  char value[20];
  FancyPassport passport = {0};

  while (!feof(fp) && getc(fp) != '\n') {
    memset(key, 0, 4);
    memset(value, 0, 20);
    fseek(fp, -1, SEEK_CUR); // Un-eat the previous char because we need it.
    fgets(key, KEY_SIZE, fp);

    fscanf(fp, ":%s", value);  // Eat the colon, value
    getc(fp);  // Eat white space

    if (strcmp(key, "byr") == 0) passport.byr = atoi(value);
    else if (strcmp(key, "iyr") == 0) passport.iyr = atoi(value);
    else if (strcmp(key, "eyr") == 0) passport.eyr = atoi(value);
    else if (strcmp(key, "hgt") == 0) passport.hgt = parse_height(value);
    else if (strcmp(key, "hcl") == 0) {
      if (strlen(value) != HAIR_COLOR_SIZE - 1) continue;  // Leave it empty
      strncpy(passport.hcl, value, HAIR_COLOR_SIZE - 1);
    }
    else if (strcmp(key, "ecl") == 0) passport.ecl = parse_eye_color(value);
    else if (strcmp(key, "pid") == 0) {
      if (strlen(value) != PID_SIZE - 1) continue;  // Leave it empty
      strncpy(passport.pid, value, PID_SIZE - 1);
    } 
    else if (strcmp(key, "cid") == 0) continue;
    else {
      printf("Unrecognized key: %s\n", key);
    }
  }

  return passport;
}

FancyPassport* parse_fancy_passports(const char* filename, int* count) {
  FILE* fp;
  fp = fopen(filename, "r");
  if (fp == NULL) {
    printf("Couldn't open file.\n");
    exit(EXIT_FAILURE);
  }

  *count = count_passports(fp);
  FancyPassport* passes = (FancyPassport*)malloc(sizeof(FancyPassport) * *count);

  for (int i = 0; i < *count; i++) {
    passes[i] = parse_fancy_passport(fp);
  }

  fclose(fp);
  return passes;
}

/// Checks whether a hair color is valid.
static bool valid_hair_color(char* color) {
  if (color[0] != '#') return false;
  for (int i = 1; color[i]; i++) {
    if ((color[i] < '0' || color[i] > '9') && (color[i] < 'a' || color[i] > 'f')) {
      return false;
    }
  }
  return true;
}

/// Checks whether a PID is valid.
static bool valid_pid(char* value) {
  if (strlen(value) != PID_SIZE - 1) return false;
  for (int i = 0; value[i]; i++) {
    if (value[i] < '0' || value[i] > '9') return false;
  }
  return true;
}

/// Finger-saving macro for part2: increment the invalids and continue
#define INC_BAD {invalid++; continue;}

int part2(FancyPassport* passes, int count) {
  int invalid = 0;
  for (int i = 0; i < count; i++) {
    FancyPassport p = passes[i];

    if (p.byr < 1920 || p.byr > 2002) INC_BAD
    if (p.iyr < 2010 || p.iyr > 2020) INC_BAD
    if (p.eyr < 2020 || p.eyr > 2030) INC_BAD
    if (p.hgt.units == HT_BAD) INC_BAD
    if (p.hgt.units == HT_CM && (p.hgt.value < 150 || p.hgt.value > 193)) INC_BAD
    if (p.hgt.units == HT_IN && (p.hgt.value < 59 || p.hgt.value > 76)) INC_BAD
    if (!valid_hair_color(p.hcl)) INC_BAD
    if (p.ecl == EYE_BAD) INC_BAD
    if (!valid_pid(p.pid)) INC_BAD
  }
  return count - invalid;
}

int day4() {
  int count;
  SimplePassport* passes = parse_simple_passports("data/day4.txt", &count);
  printf("====== Day 4 ======\n");
  printf("Part 1: %d\n", part1(passes, count));
  free(passes);

  count = 0;
  FancyPassport* passes2 = parse_fancy_passports("data/day4.txt", &count);
  printf("Part 2: %d\n", part2(passes2, count));
  free(passes2);
  return EXIT_SUCCESS;
}