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

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!

Comments

[Benjamin Trent]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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))),
    }
}