advent-of-code-2023/advent-of-code/2023/04/1.rkt

#lang racket

(require "../lib/obj.rkt")

(define (get-lines fp)
  (let loop ((lines '()))
    (define l (read-line fp))
    (if (eof-object? l)
      (reverse lines)
      (loop (cons l lines)))))

(define fp (open-input-file "input"))

(define lines (get-lines fp))

(define (strip-head s)
  (string-trim (cadr (string-split s ":"))))

(set! lines (map strip-head lines))

(define make-card (obj-maker 'win-nums 'nums))

(define (parse-card s)
  (define lst (string-split s "|"))
  (define win-nums (map string->number (string-split (car lst))))
  (define nums (map string->number (string-split (cadr lst))))
  (make-card win-nums nums))

(define (point card)
  (define wins (length (filter (lambda (x) (member x (card 'win-nums))) (card 'nums))))
  (if (= wins 0)
    0
    (expt 2 (- wins 1))))

(apply + (map point (map parse-card lines)))