Paste: AoC 2025 day 4

Author: annikapaprika
Mode: factor
Date: Thu, 4 Dec 2025 20:44:55
Plain Text | 
USING: aoc.matrices combinators kernel math math.matrices
sequences ;
IN: 2025.04

: parse ( lines -- m ) [ [ CHAR: @ = ] { } map-as ] map ;

: removable-rolls-of-paper ( m -- m' )
    [ 1 0 ? ] matrix-map neighbor-sum [ 4 < ] matrix-map ;

: part-1 ( m -- n )
    dup removable-rolls-of-paper [ and ] matrix-2count ;

: remove-rolls-of-paper ( m -- m' )
    dup removable-rolls-of-paper [ not and ] matrix-2map ;

: part-2 ( m -- n )
    dup [ remove-rolls-of-paper ] to-fixed-point
    [ xor ] matrix-2count ;

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