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refactor quicksort example

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Folkert 2021-05-08 23:18:59 +02:00
parent a99ba56eba
commit 4e57b3b0d7
1 changed files with 51 additions and 51 deletions
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102
examples/quicksort/Quicksort.roc
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@ -4,56 +4,56 @@ app "quicksort"
provides [ quicksort ] to base
quicksort = \originalList ->
quicksortHelp : List (Num a), Nat, Nat -> List (Num a)
quicksortHelp = \list, low, high ->
if low < high then
when partition low high list is
Pair partitionIndex partitioned ->
partitioned
|> quicksortHelp low (partitionIndex - 1)
|> quicksortHelp (partitionIndex + 1) high
else
list
partition : Nat, Nat, List (Num a) -> [ Pair Nat (List (Num a)) ]
partition = \low, high, initialList ->
when List.get initialList high is
Ok pivot ->
when partitionHelp (low - 1) low initialList high pivot is
Pair newI newList ->
Pair (newI + 1) (swap (newI + 1) high newList)
Err _ ->
Pair (low - 1) initialList
partitionHelp : Nat, Nat, List (Num c), Nat, (Num c) -> [ Pair Nat (List (Num c)) ]
partitionHelp = \i, j, list, high, pivot ->
if j < high then
when List.get list j is
Ok value ->
if value <= pivot then
partitionHelp (i + 1) (j + 1) (swap (i + 1) j list) high pivot
else
partitionHelp i (j + 1) list high pivot
Err _ ->
Pair i list
else
Pair i list
swap : Nat, Nat, List a -> List a
swap = \i, j, list ->
when Pair (List.get list i) (List.get list j) is
Pair (Ok atI) (Ok atJ) ->
list
|> List.set i atJ
|> List.set j atI
_ ->
[]
n = List.len originalList
quicksortHelp originalList 0 (n - 1)
quicksortHelp : List (Num a), Nat, Nat -> List (Num a)
quicksortHelp = \list, low, high ->
if low < high then
when partition low high list is
Pair partitionIndex partitioned ->
partitioned
|> quicksortHelp low (partitionIndex - 1)
|> quicksortHelp (partitionIndex + 1) high
else
list
partition : Nat, Nat, List (Num a) -> [ Pair Nat (List (Num a)) ]
partition = \low, high, initialList ->
when List.get initialList high is
Ok pivot ->
when partitionHelp (low - 1) low initialList high pivot is
Pair newI newList ->
Pair (newI + 1) (swap (newI + 1) high newList)
Err _ ->
Pair (low - 1) initialList
partitionHelp : Nat, Nat, List (Num c), Nat, (Num c) -> [ Pair Nat (List (Num c)) ]
partitionHelp = \i, j, list, high, pivot ->
if j < high then
when List.get list j is
Ok value ->
if value <= pivot then
partitionHelp (i + 1) (j + 1) (swap (i + 1) j list) high pivot
else
partitionHelp i (j + 1) list high pivot
Err _ ->
Pair i list
else
Pair i list
swap : Nat, Nat, List a -> List a
swap = \i, j, list ->
when Pair (List.get list i) (List.get list j) is
Pair (Ok atI) (Ok atJ) ->
list
|> List.set i atJ
|> List.set j atI
_ ->
[]