2 files changed, 79 insertions, 0 deletions
diff --git a/2024/aoc-utils.scm b/2024/aoc-utils.scm
new file mode 100644
index 0000000..6b57aa5
--- /dev/null
+++ b/2024/aoc-utils.scm
@@ -0,0 +1,11 @@
+(define-module (aoc-utils)
+  #:use-module (srfi srfi-1)
+  #:use-module (srfi srfi-9)
+  #:use-module (ice-9 regex)
+  #:use-module (ice-9 rdelim)
+  #:export (file->list))
+
+(define (file->list filename)
+  (let ((lines (string-split (call-with-input-file filename read-string) #\Newline)))
+    ; Remove EOF token
+    (take lines (1- (length lines)))))
diff --git a/2024/day01/main.scm b/2024/day01/main.scm
new file mode 100755
index 0000000..9334264
--- /dev/null
+++ b/2024/day01/main.scm
@@ -0,0 +1,68 @@
+#!/usr/bin/guile -s
+!#
+
+(add-to-load-path (format #f "~a/2024" (getcwd)))
+(add-to-load-path (format #f "~a/.." (dirname (current-filename))))
+
+(use-modules
+ (aoc-utils)
+ (srfi srfi-1)
+ (srfi srfi-9)
+ (ice-9 regex))
+
+(define line-rx "([0-9]+)\\s+([0-9]+)")
+
+(define (match-line line)
+  (let ((match (string-match line-rx line)))
+    (list (string->number (match:substring match 1))
+          (string->number (match:substring match 2)))))
+
+(define (first-sorted-list l)
+  (sort (map (lambda (pair) (car pair)) l) <))
+(define (second-sorted-list l)
+  (sort (map (lambda (pair) (car (cdr pair))) l) <))
+
+(define (part1 lines)
+  (let* ((lines (map (lambda (line) (match-line line))
+                     lines))
+         (first-list (first-sorted-list lines))
+         (second-list (second-sorted-list lines)))
+    (fold (lambda (pair acc)
+            (+ acc (abs (- (first pair) (second pair)))))
+          0
+          (zip first-list second-list))))
+
+(define (make-counter l)
+  (let ((h (make-hash-table)))
+    (for-each (lambda (n)
+                (if (hash-ref h n)
+                    (hash-set! h n (1+ (hash-ref h n)))
+                    (hash-set! h n 1)))
+              l)
+    h))
+
+(define (part2 lines)
+  (let* ((lines (map (lambda (line) (match-line line)) lines))
+         (first-list (map (lambda (pair) (car pair)) lines))
+         (second-list (map (lambda (pair) (car (cdr pair))) lines))
+         (counter-map (make-counter second-list)))
+    (fold (lambda (n acc)
+            ;; (display n) (display "-") (display acc) (newline)
+            (+ (* n (if (hash-ref counter-map n)
+                        (hash-ref counter-map n)
+                        0))
+               acc))
+          0
+          first-list)))
+
+
+(define (main)
+  (let ((lines (file->list "input.txt")))
+    (display "Part1: ")
+    (display (part1 lines))
+    (newline)
+    (display "Part2: ")
+    (display (part2 lines))
+    (newline)))
+
+(main)