retroforth/example/advent-of-code-2020-day-4.retro
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2021-06-04 13:54:21 +00:00

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Forth

# Day 4: Passport Processing
You arrive at the airport only to realize that you grabbed your
North Pole Credentials instead of your passport. While these
documents are extremely similar, North Pole Credentials aren't
issued by a country and therefore aren't actually valid
documentation for travel in most of the world.
It seems like you're not the only one having problems, though;
a very long line has formed for the automatic passport scanners,
and the delay could upset your travel itinerary.
Due to some questionable network security, you realize you might
be able to solve both of these problems at the same time.
The automatic passport scanners are slow because they're having
trouble detecting which passports have all required fields. The
expected fields are as follows:
byr (Birth Year)
iyr (Issue Year)
eyr (Expiration Year)
hgt (Height)
hcl (Hair Color)
ecl (Eye Color)
pid (Passport ID)
cid (Country ID)
Passport data is validated in batch files (your puzzle input).
Each passport is represented as a sequence of key:value pairs
separated by spaces or newlines. Passports are separated by
blank lines.
Here is an example batch file containing four passports:
ecl:gry pid:860033327 eyr:2020 hcl:#fffffd
byr:1937 iyr:2017 cid:147 hgt:183cm
iyr:2013 ecl:amb cid:350 eyr:2023 pid:028048884
hcl:#cfa07d byr:1929
hcl:#ae17e1 iyr:2013
eyr:2024
ecl:brn pid:760753108 byr:1931
hgt:179cm
hcl:#cfa07d eyr:2025 pid:166559648
iyr:2011 ecl:brn hgt:59in
The first passport is valid - all eight fields are present. The
second passport is invalid - it is missing hgt (the Height field).
The third passport is interesting; the only missing field is cid,
so it looks like data from North Pole Credentials, not a passport
at all! Surely, nobody would mind if you made the system
temporarily ignore missing cid fields. Treat this "passport" as
valid.
The fourth passport is missing two fields, cid and byr. Missing
cid is fine, but missing any other field is not, so this passport
is invalid.
According to the above rules, your improved system would report
2 valid passports.
Count the number of valid passports - those that have all
required fields. Treat cid as optional. In your batch file, how
many passports are valid?
----
I first create two data structures: an array of passport
strings, and a buffer to hold the current passport being
read in.
The `Passports` array is constructed using the `buffer:`
words.
~~~
'Passports d:create #1024 allot
'Passport d:create #1024 allot
&Passports n:inc buffer:set
~~~
Importing the passports is pretty easy. There's a blank line after
each entry is complete, so just gather the text until then, then
save the string and record a pointer into the `Passports` listing.
~~~
:add-data '_ s:append &Passport s:append &Passport s:copy ;
:record drop &Passport s:keep buffer:add #0 !Passport ;
:completed? dup s:length n:zero? ;
:finish &Passports n:inc s:length !Passports ;
:passports:load
[ completed? [ record ]
[ add-data ] choose ] file:for-each-line finish ;
'input-day-4 passports:load
~~~
Now that the passport database is loaded, we can simply check
each entry for the required fields, increasing a counter for
each one that proves valid.
~~~
:valid?
[ [ 'byr: s:contains/string? ]
[ 'iyr: s:contains/string? ]
[ 'eyr: s:contains/string? ] tri and and ]
[ [ 'hgt: s:contains/string? ]
[ 'hcl: s:contains/string? ]
[ 'ecl: s:contains/string? ] tri and and ]
[ 'pid: s:contains/string? ] tri and and ;
#0 &Passports [ valid? [ n:inc ] if ] a:for-each
~~~
----
# Part Two
The line is moving more quickly now, but you overhear airport
security talking about how passports with invalid data are
getting through. Better add some data validation, quick!
You can continue to ignore the cid field, but each other
field has strict rules about what values are valid for
automatic validation:
byr (Birth Year) - four digits; at least 1920 and at most 2002.
iyr (Issue Year) - four digits; at least 2010 and at most 2020.
eyr (Expiration Year) - four digits; at least 2020 and at most 2030.
hgt (Height) - a number followed by either cm or in:
If cm, the number must be at least 150 and at most 193.
If in, the number must be at least 59 and at most 76.
hcl (Hair Color) - a # followed by exactly six characters 0-9 or a-f.
ecl (Eye Color) - exactly one of: amb blu brn gry grn hzl oth.
pid (Passport ID) - a nine-digit number, including leading zeroes.
cid (Country ID) - ignored, missing or not.
Your job is to count the passports where all required fields
are both present and valid according to the above rules. Here
are some example values:
byr valid: 2002
byr invalid: 2003
hgt valid: 60in
hgt valid: 190cm
hgt invalid: 190in
hgt invalid: 190
hcl valid: #123abc
hcl invalid: #123abz
hcl invalid: 123abc
ecl valid: brn
ecl invalid: wat
pid valid: 000000001
pid invalid: 0123456789
Here are some invalid passports:
... snipped ...
Count the number of valid passports - those that have all
required fields and valid values. Continue to treat cid as
optional. In your batch file, how many passports are valid?
----
I'll start this by defining some things. An array of valid eye
colors, and some words for validating ranges for particular
fields.
~~~
{ 'amb 'blu 'brn 'gry 'hzl 'oth 'grn } 'EYE-COLORS const
:birth-year? s:to-number #1920 #2002 n:between? ;
:issue-year? s:to-number #2010 #2020 n:between? ;
:expire-year? s:to-number #2020 #2030 n:between? ;
:height-imperial? #59 #76 n:between? ;
:height-metric? #150 #193 n:between? ;
~~~
I'll store a count of the number of valid fields in a variable.
~~~
'Valid var
:record-result [ &Valid v:inc ] if ;
~~~
Then I implement the checks for each field.
~~~
:process-byr [ s:length #4 eq? ]
[ birth-year? ] bi and record-result ;
:process-iyr [ s:length #4 eq? ]
[ issue-year? ] bi and record-result ;
:process-eyr [ s:length #4 eq? ]
[ expire-year? ] bi and record-result ;
:process-hgt [ [ c:digit? ] s:filter s:to-number ]
[ #2 s:right 'cm s:eq? ] bi
[ height-metric? ] [ height-imperial? ] choose record-result ;
:process-hcl [ fetch $# eq? ]
[ s:length #7 eq? ]
[ [ 'abcdef0123456789 swap s:contains/char? ] s:filter s:length #6 eq? ] tri
and and record-result ;
:process-ecl EYE-COLORS a:contains/string? record-result ;
:process-pid [ s:length #9 eq? ]
[ [ c:digit? ] s:filter s:length #9 eq? ] bi and record-result ;
~~~
Processing each passport is just a matter of splitting it up
into fields and checking each. The final number of valid
passports will be left on the stack.
~~~
:split s:trim ASCII:SPACE s:tokenize ;
:get-field $: s:tokenize [ ] a:for-each swap ;
:validate-field 'byr [ process-byr ] s:case
'iyr [ process-iyr ] s:case
'eyr [ process-eyr ] s:case
'hgt [ process-hgt ] s:case
'hcl [ process-hcl ] s:case
'ecl [ process-ecl ] s:case
'pid [ process-pid ] s:case
drop-pair ;
:validate #0 !Valid split [ get-field validate-field ] a:for-each ;
#0 &Passports [ dup valid? [ validate @Valid #7 eq? [ n:inc ] if ] [ drop ] choose ] a:for-each
~~~