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adventofcode
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Day 02. I'll add comments later.

This commit is contained in:
Jonathan Chan 2019-12-02 01:25:42 -08:00
parent a14466c2c2
commit 7a1101c69f
2 changed files with 105 additions and 0 deletions
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input/02.txt Normal file
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1,0,0,3,1,1,2,3,1,3,4,3,1,5,0,3,2,1,9,19,1,10,19,23,2,9,23,27,1,6,27,31,2,31,9,35,1,5,35,39,1,10,39,43,1,10,43,47,2,13,47,51,1,10,51,55,2,55,10,59,1,9,59,63,2,6,63,67,1,5,67,71,1,71,5,75,1,5,75,79,2,79,13,83,1,83,5,87,2,6,87,91,1,5,91,95,1,95,9,99,1,99,6,103,1,103,13,107,1,107,5,111,2,111,13,115,1,115,6,119,1,6,119,123,2,123,13,127,1,10,127,131,1,131,2,135,1,135,5,0,99,2,14,0,0

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src/02.rkt Normal file
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#lang racket
(require "../lib.rkt")
(define input
(map string->number (string-split (car (problem-input 2)) ",")))
(define (input-nv nv)
(append (list (car input) (first nv) (second nv)) (cdddr input)))
(define (exec pointer program)
(let* ([opcode (list-ref program pointer)]
[val1 (list-ref program (list-ref program (+ pointer 1)))]
[val2 (list-ref program (list-ref program (+ pointer 2)))]
[val3 (list-ref program (+ pointer 3))]
[next-program
(cond [(= opcode 1)
(list-set program val3 (+ val1 val2))]
[(= opcode 2)
(list-set program val3 (* val1 val2))]
[else program])])
(if (= opcode 99)
next-program
(exec (+ pointer 4) next-program))))
(define part1
(car (exec 0 (input-nv '(12 2)))))
(define part2
(let* ([nounverbs (cartesian-product (range 100) (range 100))]
[outputs (map (λ (nv) (car (exec 0 (input-nv nv)))) nounverbs)]
[nounverb (list-ref nounverbs (index-of outputs 19690720))]
[noun (first nounverb)]
[verb (second nounverb)])
(+ (* 100 noun) verb)))
(show-solution part1 part2)
;;;; ALTERNATE SOLUTION
(define part2-input
(append (list (car input) 'noun 'verb '(+ noun verb)) (cddddr input)))
(define (exec-sym pointer program)
(let* ([opcode (list-ref program pointer)]
[val1 (list-ref program (list-ref program (+ pointer 1)))]
[val2 (list-ref program (list-ref program (+ pointer 2)))]
[val3 (list-ref program (+ pointer 3))]
[next-program
(cond [(= opcode 1)
(list-set program val3 `(+ ,val1 ,val2))]
[(= opcode 2)
(list-set program val3 `(* ,val1 ,val2))]
[else program])])
(if (= opcode 99)
next-program
(exec-sym (+ pointer 4) next-program))))
(define part2-partial
(car (exec-sym 4 part2-input)))
(define (simplify expr)
(match expr
; (op n1 n2 e) -> (simplify (op (n1 `op` n2) (simplify e)))
[(or `(,op (,op ,(? number? n1) ,e) ,(? number? n2))
`(,op (,op ,e ,(? number? n1)) ,(? number? n2))
`(,op ,(? number? n1) (,op ,(? number? n2) ,e))
`(,op ,(? number? n1) (,op ,e ,(? number? n2))))
(let ([opfun (match op ['+ +] ['* *])])
(simplify `(,op ,(opfun n1 n2) ,(simplify e))))]
; (op e1 e2 s) -> (op (simplify (op e1 e2)) s)
[(or `(,op (,op ,e1 ,(? symbol? s)) ,e2)
`(,op (,op ,(? symbol? s) ,e1) ,e2)
`(,op ,e1 (,op ,e2 ,(? symbol? s)))
`(,op ,e1 (,op ,(? symbol? s) ,e2)))
`(,op ,(simplify `(,op ,e1 ,e2)) ,s)]
; (* (+ n1 e) n2) -> (simplify (+ (n1 * n2) (simplify (* n1 e))))
[(or `(* (+ ,(? number? n2) ,e) ,(? number? n1))
`(* (+ ,e ,(? number? n2)) ,(? number? n1))
`(* ,(? number? n1) (+ ,(? number? n2) ,e))
`(* ,(? number? n1) (+ ,e ,(? number? n2))))
(simplify `(+ ,(* n1 n2) ,(simplify `(* ,n1 ,e))))]
[`(* ,(? number? n1) ,(? number? n2)) (* n1 n2)]
[`(+ ,(? number? n1) ,(? number? n2)) (+ n1 n2)]
[`(+ ,l ,r) `(+ ,(simplify l) ,(simplify r))]
[`(* ,l ,r) `(* ,(simplify l) ,(simplify r))]
[(? number? n) n]
[(? symbol? s) s]))
; (+ (+ 520625 (* 270000 noun)) verb) = 19690720
(define part2-alt
(let ([simplified (simplify part2-partial)])
(match simplified
[`(+ (+ ,n1 (* ,n2 noun)) verb)
(let* ([dividend (- 19690720 n1)]
[modulus n2]
[noun (quotient dividend modulus)]
[verb (remainder dividend modulus)])
(+ (* 100 noun) verb))])))