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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 (all-decresing? report)
(equal? report (sort report >)))
(define (all-incrising? report)
(equal? report (sort report <)))
(define (safe-head? report)
(if (>=(length report) 2)
(let ((diff (abs (- (first report) (second report)))))
(and (<= diff 3) (>= diff 1)))
#t))
(define (safe-difference? report)
(cond ((not (safe-head? report)) #f)
((null? report) #t)
(else (safe-difference? (cdr report)))))
(define (safe-report? report)
(and (or (all-incrising? report)
(all-decresing? report))
(safe-difference? report)))
(define (part1 lines)
(let ((reports (lines->number-list lines)))
(fold + 0 (map (lambda (report) (if (safe-report? report)
1
0)) reports))))
(define (indexes report)
(let ((retval '()))
(do ((i (1- (length report)) (1- i)))
((< i 0))
(set! retval (cons i retval)))
retval))
(define (gen-reports report)
(cons report (map (lambda (idx)
(remove-nth report idx)) (indexes report))))
(define (safe-report-with-toleration? report)
(any safe-report? (gen-reports report)))
(define (part2 lines)
(let ((reports (lines->number-list lines)))
(apply + (map (lambda (r)
(if (safe-report-with-toleration? r)
1
0)) reports))))
(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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