AoC day 10, Smalltalk

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

Array extend [
    incAt: key [
        ^self at: key put: (self at: key) + 1
    ]
]

" Read and sort input "
adapt := SortedCollection with: 1.
stdin linesDo: [ :line | adapt add: (line asNumber + 1) ].

" Calculate difference counts "
counts := Array withAll: #(0 0 1).
(1 to: adapt size - 1) do: [ :i |
    counts incAt: (adapt at: i+1) - (adapt at: i)
].

stdout nextPutAll: 'Part 1: ', ((counts at: 3) * (counts at: 1)) asString; nl.

" Part 2 -- Dynamic Programming "
table := Array new: adapt last.
table at: 1 put: 1.

" Progressively build table using previous calculated values "
adapt do: [ :i |
    ((table at: i) = nil) ifTrue: [
        conx := adapt select: [ :a | a between: (i-3) and: (i-1) ].
        sum  := conx inject: 0 into: [ :a :b | a + (table at: b) ].
        table at: i put: sum.
    ]
].

stdout nextPutAll: 'Part 2: ', table last asString; nl.