AoC day 3, part 2 (smalltalk)

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

" Some conventient covering extensions: "
String extend [
    asRadix: rad [ ^Number readFrom: (ReadStream on: self) radix: rad ]
]

" Extending Set with a method to do the work for this script "
Set extend [
    filter: wantMin [
        | i |

        i := 1.
        [self size > 1] whileTrue: [
            | sets sort |

            sets := Dictionary from: { $0 -> Set new. $1 -> Set new }.
            self do: [ :num | (sets at: (num at: i)) add: num ].

            sort := sets associations sorted: [:a :b |
                        ((a value size > b value size) | (a key > b key)) xor: wantMin
                    ].

            self removeAll: (sort first value).

            i := i + 1.
        ].

        ^self anyOne
    ]
]


"
| Mainline
"
input := stdin lines contents.

oxyCo2 := #(true false) collect: [ :mode | (input asSet filter: mode) asRadix: 2 ].

('Part 2: %1' % {(oxyCo2 at: 1) * (oxyCo2 at: 2)}) displayNl.