This was bugging me last night, as I still didn’t like the solution. What
about something like:
func selectionSort(_ originalArray: [Int]) -> [Int] {
var array = originalArray
for index in 0..<array.count {
let minIndex = array.indices.clamped(to:
index..<x.count).min(isOrderedBefore: { array[$0] < array[$1] })
if index != minIndex {
swap(&array[index], &array[minIndex!])
}
}
return array
}
On 6/29/16, 7:12 PM, "[email protected] on behalf of Tod Cunningham
via swift-users" <[email protected] on behalf of
[email protected]> wrote:
Was trying to using some functional programming concepts while also using as
little memory as possible. The big advantage of using a selections sort is
that it sorts w/o having to allocation additional memory. This still violates
that, but it’s closer. :)
func selectionSort(_ array: inout [Int]) {
for index in 0..<array.count {
// .1 is value .0 is the index on the enumeration
let minElement =
array.enumerated().dropFirst(index).min(isOrderedBefore: { $0.1 < $1.1 } )
if index != minElement!.0 {
swap(&array[index], &array[minElement!.0])
}
}
}
or using recursion:
func selectionSort(_ array: inout [Int], index: Int = 0) {
if index < array.count {
// .1 is value .0 is the index on the enumeration
let minElement = array.indexed().dropFirst(index).min(isOrderedBefore:
{ $0.1 < $1.1 } )
if index != minElement!.0 {
swap(&array[index], &array[minElement!.0])
}
selectionSort(&array, index: index+1)
}
}
On 6/28/16, 10:58 PM, "[email protected] on behalf of Erica Sadun
via swift-users" <[email protected] on behalf of
[email protected]> wrote:
>
> On Jun 28, 2016, at 8:18 PM, Dan Loewenherz via swift-users
> <[email protected]> wrote:
>
> I’m not sure if you wanted to stick with the pure functional approach, but
> here’s an alternative that uses Range<Int> to take care of most of the work.
>
> func selectionSort(_ array: [Int]) -> [Int] {
> guard let minValue = array.min(), let index = array.index(of: minValue)
> else {
> return []
> }
>
> let ranges = [0..<index, index.advanced(by: 1)..<array.endIndex]
> return [minValue] + selectionSort(ranges.flatMap { array[$0] })
> }
>
Most everyone is doing two passes, one to get the minimum value, another to get
its index.
I aesthetically prefer using enumerate to do both at once.
-- E
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