AoC 2023, day 4 (Smalltalk)

#!/usr/local/bin/gst -q

Collection extend [
    at: idx inc: val [ ^self at: idx put: val + (self at: idx) ]
    sum              [ ^self inject: 0 into: [:a :b | a + b]   ]
]

" Convert input into a list of number of wins on each card: "
cardWins := stdin lines contents collect: [ :line |
                parts := line subStrings: ':|'.
                wins  := parts second subStrings asSet.
                parts third subStrings count: [:n | wins includes: n].
            ].

" Note: using floor to handle the 0 wins case, as 2^-1 = 1/2 "
part1 := (cardWins collect: [:n | (2 raisedTo: n - 1) floor]) sum.

" Part 2: Start with one of each card, propagate wins forwards: "
cards := Array new: cardWins size withAll: 1.
cards keysAndValuesDo: [ :card :num |
    (card + 1 to: card + (cardWins at: card)) do: [:i | cards at: i inc: num].
].

('Part 1: %1' % {part1}) displayNl.
('Part 2: %1' % {cards sum}) displayNl.