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#!/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)
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