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69 lines
2.2 KiB
Plaintext
69 lines
2.2 KiB
Plaintext
app "quicksort" packages { base: "./platform" } provides [ quicksort ] to base
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quicksort : List Int * -> List Int *
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quicksort = \originalList -> helper originalList
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helper : List Int * -> List Int *
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helper = \originalList ->
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quicksortHelp : List (Num a), Nat, Nat -> List (Num a)
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quicksortHelp = \list, low, high ->
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if low < high then
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when partition low high list is
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Pair partitionIndex partitioned ->
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partitioned
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|> quicksortHelp low (partitionIndex - 1)
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|> quicksortHelp (partitionIndex + 1) high
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else
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list
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swap : Nat, Nat, List a -> List a
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swap = \i, j, list ->
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when Pair (List.get list i) (List.get list j) is
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Pair (Ok atI) (Ok atJ) ->
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list
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|> List.set i atJ
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|> List.set j atI
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_ ->
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[]
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partition : Nat, Nat, List (Num a) -> [ Pair Nat (List (Num a)) ]
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partition = \low, high, initialList ->
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when List.get initialList high is
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Ok pivot ->
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when partitionHelp (low - 1) low initialList high pivot is
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Pair newI newList ->
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Pair (newI + 1) (swap (newI + 1) high newList)
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Err _ ->
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Pair (low - 1) initialList
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partitionHelp : Nat, Nat, List (Num a), Nat, (Num a) -> [ Pair Nat (List (Num a)) ]
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partitionHelp = \i, j, list, high, pivot ->
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if j < high then
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when List.get list j is
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Ok value ->
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if value <= pivot then
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partitionHelp (i + 1) (j + 1) (swap (i + 1) j list) high pivot
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else
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partitionHelp i (j + 1) list high pivot
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Err _ ->
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Pair i list
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else
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Pair i list
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result = quicksortHelp originalList 0 (List.len originalList - 1)
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if List.len originalList > 3 then
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result
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else
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# Absolutely make the `originalList` Shared by using it again here
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# but this branch is not evaluated, so should not affect performance
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List.set originalList 0 (List.len originalList)
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