day 1

.gitignore

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+*
+!/*
+!hs/*.hs
+!rkt/*.rkt
+!pl/*.pl
+!.gitignore
+!input/*

LICENSE

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+ Copyright (C) 2021 by chayleaf <chayleaf@protonmail.com>
+
+Permission to use, copy, modify, and/or distribute this software for any purpose with or without fee is hereby granted.
+
+THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

README.md

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+# Advent of Code 2021
+
+Decided to learn 3 new languages at a time! Hopefully I will last...
+
+# Haskell
+
+```bash
+ghc -dynamic program.hs && ./program
+```
+
+# Prolog
+
+```bash
+swipl -g main file.pl
+```
+
+# Racket
+
+```bash
+racket file.rkt
+```

hs/01.1.hs

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+import System.IO
+
+main = print . snd . foldl step (Nothing, 0) . map (read :: String -> Int) . lines =<< readFile "../input/01"
+
+step (Nothing, sum) n = (Just n, sum)
+step ((Just last), sum) n = (Just n, sum +
+    (if n > last then 1 else 0))
+step :: (Maybe Int, Int) -> Int -> (Maybe Int, Int)

hs/01.2.hs

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+import System.IO
+
+main = print . snd . foldl step ([], 0) . map (read :: String -> Int) . lines =<< readFile "../input/01"
+
+step ([], sum) n = ([n], sum)
+step ([a], sum) n = ([a, n], sum)
+step ([a, b], sum) n = ([a, b, n], sum)
+step ([a, b, c], sum) n = ([b, c, n], sum + if n > a then 1 else 0)
+step :: ([Int], Int) -> Int -> ([Int], Int)

pl/01.1.pl

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+read_file(Stream, []) :-
+    at_end_of_stream(Stream).
+
+read_file(Stream, [X|L]) :-
+    \+ at_end_of_stream(Stream),
+    read_line_to_codes(Stream, C),
+    atom_chars(A, C),
+    read_file(Stream, L),
+    atom_number(A, X).
+
+main :-
+    open('../input/01', read, Stream),
+    read_file(Stream, Lines), !,
+    close(Stream),
+    step(Lines, N),
+    print(N).
+
+step([], 0).
+step([A|Tail], B) :-
+    step_(A, Tail, B).
+
+step_(_, [], 0).
+step_(A, [B|Tail], Res) :-
+    A < B,
+    step_(B, Tail, TailRes),
+    Res is TailRes + 1.
+step_(A, [B|Tail], Res) :-
+    A >= B,
+    step_(B, Tail, Res).
+

pl/01.2.pl

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+read_file(Stream, []) :-
+    at_end_of_stream(Stream).
+
+read_file(Stream, [X|L]) :-
+    \+ at_end_of_stream(Stream),
+    read_line_to_codes(Stream, C),
+    atom_chars(A, C),
+    read_file(Stream, L),
+    atom_number(A, X).
+
+main :-
+    open('../input/01', read, Stream),
+    read_file(Stream, Lines), !,
+    close(Stream),
+    step(Lines, N),
+    print(N).
+
+step([], 0).
+step([_], 0).
+step([_, _], 0).
+step([A|Tail], Res) :-
+    step1(A, Tail, Res).
+step1(A, [B|Tail], Res) :-
+    step2(A, B, Tail, Res).
+step2(A, B, [C|Tail], Res) :-
+    step_(A, B, C, Tail, Res).
+
+step_(_, _, _, [], 0).
+step_(A, B, C, [N|Tail], Res) :-
+    A < N,
+    step_(B, C, N, Tail, TailRes),
+    Res is TailRes + 1.
+step_(A, B, C, [N|Tail], Res) :-
+    A >= N,
+    step_(B, C, N, Tail, Res).
+

rkt/01.1.rkt

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+#lang racket
+
+(with-input-from-file "../input/01"
+  (lambda ()
+    (for/fold ([cnt 0]
+               [last null]
+               #:result cnt)
+              ([line (in-lines)])
+      (let ([num (string->number line)])
+        (values (cond [(null? last) cnt]
+                      [(> num last) (+ cnt 1)]
+                      [else cnt])
+                num)))))
+

rkt/01.2.rkt

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+#lang racket
+
+(with-input-from-file "../input/01"
+  (lambda ()
+    (for/fold ([cnt 0]
+               [last null]
+               #:result cnt)
+              ([line (in-lines)])
+      (let ([num (string->number line)])
+        (if (< (length last) 3)
+          (values cnt (append last (list num)))
+          (values
+            (if (> num (car last))
+              (+ cnt 1)
+              cnt)
+            (append (cdr last) (list num))))))))
+