added bubble, heap, merge, and pancake sort

DIRECTORY.md

@@ -5,3 +5,7 @@
 
 ## Sorts
   * [Quicksort](https://github.com/TheAlgorithms/OCaml/blob/master/Sorts/quicksort.ml)
+  * [Bubble sort](https://github.com/TheAlgorithms/OCaml/blob/master/Sorts/bubble_sort.ml)
+  * [Merge sort](https://github.com/TheAlgorithms/OCaml/blob/master/Sorts/heap_sort.ml)
+  * [Heap sort](https://github.com/TheAlgorithms/OCaml/blob/master/Sorts/pancake_sort.ml)
+  * [Pancake sort](https://github.com/TheAlgorithms/OCaml/blob/master/Sorts/merge_sort.ml)

Sorts/bubble_sort.ml

@@ -0,0 +1,24 @@
+let rec bubble_sort lst =
+  let aux =
+  match lst with
+  | h :: h' :: tl when h > h' ->
+    h' :: bubble_sort (h :: tl)
+  | h :: tl ->
+    h :: bubble_sort tl
+  | tl ->
+    tl
+  in
+    if lst = aux then lst
+    else bubble_sort aux
+
+(* testing the bubble sort *)
+let _ = 
+  let pp_list list = 
+    list 
+    |> List.map string_of_int
+    |> String.concat ", "
+  in
+    let list = [13; 2; 3; 14; 17; 4; 1; 5; 16; 12; 9; 10; 15; 8; 7; 11; 18; 19; 6; 20]
+    in 
+      Printf.printf "unsorted: [ %s ]\n" (pp_list list),
+      Printf.printf "sorted: [ %s ]\n" (list |> bubble_sort |> pp_list)

Sorts/heap_sort.ml

@@ -0,0 +1,41 @@
+let heap_sort arr =
+  let swap i j =
+    let t = arr.(i) in 
+    arr.(i) <- arr.(j); 
+    arr.(j) <- t
+  in
+
+  let sift k l =
+    let rec check root child =
+      if 2 * root + 1 < l then
+        let ch =
+          if child < l - 1 && arr.(child) < arr.(child + 1) then child + 1 else child in
+        if arr.(root) < arr.(ch) then (swap root ch; check ch (2 * ch + 1)) in
+    check k (2 * k + 1)
+  in
+
+  let len = Array.length arr in
+
+  for start = (len / 2) - 1 downto 0 do
+    sift start len
+  done;
+
+  for term = len - 1 downto 1 do
+    swap term 0;
+    sift 0 term;
+  done
+;;
+
+
+(* testing the heap sort *)
+let _ = 
+  let pp_arr arr = 
+    arr 
+    |> Array.map string_of_int
+    |> Array.fold_left (fun acc s -> acc ^ s ^ ", ") ""
+  in
+    let arr = [| 13; 2; 3; 14; 17; 4; 1; 5; 16; 12; 9; 10; 15; 8; 7; 11; 18; 19; 6; 20 |]
+    in 
+      Printf.printf "unsorted: [ %s ]\n" (pp_arr arr),
+      heap_sort arr,
+      Printf.printf "sorted: [ %s ]\n" (pp_arr arr);;

Sorts/merge_sort.ml

@@ -0,0 +1,38 @@
+let split list =
+  let rec aux l acc acc' =
+    match l with
+    | [] -> (acc, acc')
+    | [x] -> (x :: acc, acc')
+    | h :: h' :: t -> aux t (h :: acc) (h' :: acc')
+  in
+    aux list [] []
+
+let rec merge l l' =
+  match (l, l') with
+  | (x, []) -> x
+  | ([], x) -> x
+  | (x :: tx, y :: ty) -> 
+    if x < y then
+      x :: merge tx l'
+    else
+      y :: merge l ty
+
+let rec merge_sort list =
+  match list with
+  | [] -> []
+  | [x] -> [x]
+  | _ ->
+    let (l, l') = split list in
+    merge (merge_sort l) (merge_sort l')
+
+(* testing the merge sort *)
+let _ = 
+  let pp_list list = 
+    list 
+    |> List.map string_of_int
+    |> String.concat ", "
+  in
+    let list = [13; 2; 3; 14; 17; 4; 1; 5; 16; 12; 9; 10; 15; 8; 7; 11; 18; 19; 6; 20]
+    in 
+      Printf.printf "unsorted: [ %s ]\n" (pp_list list),
+      Printf.printf "sorted: [ %s ]\n" (list |> merge_sort |> pp_list)

Sorts/pancake_sort.ml

@@ -0,0 +1,35 @@
+let rec sorted = function
+  | [] -> (true)
+  | h :: h' :: _ when h > h' -> (false)
+  | _ :: t -> sorted t 
+
+let flip l =
+  let rec aux acc g p s = function
+    | h :: t when h > g -> aux (h :: acc) h acc t t  
+    | h :: t -> aux (h :: acc) g p s t
+    | [] -> (g, (p @ s))
+  in 
+    aux [] min_int [] l l
+
+let pancake_sort l =
+  let rec aux l s =
+    let g, l = flip l in 
+    let s = g :: s 
+    and l = List.rev l in
+    if sorted l then (l @ s)
+    else aux l s
+  in 
+    aux l []
+
+(* testing the pancake sort *)
+let _ = 
+  let pp_list list = 
+    list 
+    |> List.map string_of_int
+    |> String.concat ", "
+  in
+    let list = [13; 2; 3; 14; 17; 4; 1; 5; 16; 12; 9; 10; 15; 8; 7; 11; 18; 19; 6; 20]
+    in 
+      Printf.printf "unsorted: [ %s ]\n" (pp_list list),
+      Printf.printf "sorted: [ %s ]\n" (list |> pancake_sort |> pp_list)
+