54 lines
1.5 KiB
EmacsLisp
54 lines
1.5 KiB
EmacsLisp
;; Advent of Code 2020 - Day 2
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(require 'cl-lib)
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(require 'f)
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(require 'ht)
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(require 's)
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(require 'seq)
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(defvar day2/input
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;; This one was too large to inline.
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(s-lines (f-read "/tmp/aoc/day2.txt")))
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(defun day2/count-letters (password)
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(let ((table (ht-create)))
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(cl-loop for char across password
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for current = (ht-get table char)
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do (ht-set table char
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(if current (+ 1 current) 1)))
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table))
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(defun day2/parse (input)
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(let* ((split (s-split " " input))
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(range (s-split "-" (car split))))
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(list (string-to-number (car range))
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(string-to-number (cadr range))
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(string-to-char (cadr split))
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(caddr split))))
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(defun day2/count-with-validation (func)
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(length (-filter
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(lambda (password)
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(and (not (seq-empty-p password))
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(apply func (day2/parse password))))
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day2/input)))
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;; Puzzle 1
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(defun day2/validate-oldjob (min max char password)
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(let ((count (ht-get (day2/count-letters password) char)))
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(when count
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(and (>= count min)
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(<= count max)))))
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(message "Solution to day2/1: %s"
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(day2/count-with-validation #'day2/validate-oldjob))
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;; Puzzle 2
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(defun day2/validate-toboggan (pos1 pos2 char password)
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(xor (= char (aref password (- pos1 1)))
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(= char (aref password (- pos2 1)))))
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(message "Solution to day2/2: %s"
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(day2/count-with-validation #'day2/validate-toboggan))
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