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Use problem #11 for #13 and write #11 in terms of pack from #09

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Joseph Ferano 2023-01-04 12:30:14 +07:00
parent e869be4852
commit 6a59fdf97f
1 changed files with 27 additions and 14 deletions
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@ -198,7 +198,6 @@ let rec pack list =
then f (x::acc1) acc2 tail then f (x::acc1) acc2 tail
else f [] ((x::acc1)::acc2) tail else f [] ((x::acc1)::acc2) tail
in f [] [] list |> List.rev in f [] [] list |> List.rev
#+end_src #+end_src
@ -250,18 +249,23 @@ type 'a rle =
**** Solution **** Solution
#+begin_src ocaml #+begin_src ocaml
let encode = function let rec pack list =
| [] -> [] let rec f acc1 acc2 = function
| list -> | [] -> []
let rec f (count, elem) acc2 = function | [x] -> (x::acc1)::acc2
| [] -> [] | x::(y::xs as tail) ->
| [x] when count = 0 -> (One x)::acc2 if x = y
| [x] -> (Many (count + 1, x))::acc2 then f (x::acc1) acc2 tail
| x::(y::xs as tail) when x = y -> f (count + 1, elem) acc2 tail else f [] ((x::acc1)::acc2) tail
| x::(y::xs as tail) when count = 0 -> f (0, y) ((One x)::acc2) tail in f [] [] list |> List.rev
| x::(y::xs as tail) -> f (0, y) ((Many (count + 1, x))::acc2) tail
in f (0, List.nth list 0) [] list |> List.rev
let encode list =
let packed = pack list
in packed |>
List.map (function
| [] -> invalid_arg "List should not be empty"
| [x] -> One x
| x::xs as l -> Many (List.length l, x))
#+end_src #+end_src
@ -306,7 +310,17 @@ result list by replacing the singleton lists (1 X) by X.
**** Solution **** Solution
#+begin_src ocaml #+begin_src ocaml
let encode = function
| [] -> []
| list ->
let rec f (count, elem) acc2 = function
| [] -> []
| [x] when count = 0 -> (One x)::acc2
| [x] -> (Many (count + 1, x))::acc2
| x::(y::xs as tail) when x = y -> f (count + 1, elem) acc2 tail
| x::(y::xs as tail) when count = 0 -> f (0, y) ((One x)::acc2) tail
| x::(y::xs as tail) -> f (0, y) ((Many (count + 1, x))::acc2) tail
in f (0, List.nth list 0) [] list |> List.rev
#+end_src #+end_src
@ -368,4 +382,3 @@ let drop list num =
in f (num,[]) list |> List.rev in f (num,[]) list |> List.rev
#+end_src #+end_src