Add bubble sort

Sorts/bubble_sort.ml

@@ -0,0 +1,37 @@
+(* Bubble sort - recursive version with tail-recursion *)
+(* See https://en.wikipedia.org/wiki/Bubble_sort *)
+let bubble_sort l = 
+  let n = (List.length l) - 1 in
+  let rec bubble_sort_rec arr res n = 
+    match arr with
+    | [] -> if n > 0 then bubble_sort_rec res [] (n - 1) else res 
+    | x :: [] -> if n > 0 then bubble_sort_rec (res @ [x]) [] (n - 1) else (res @ [x])
+    | x1 :: x2 :: xs -> 
+        begin
+          if x1 <= x2 then
+            (bubble_sort_rec (x2 :: xs) (res @ [x1]) n)
+          else 
+            (bubble_sort_rec (x1 :: xs) (res @ [x2]) n)
+        end
+  in bubble_sort_rec l [] (n+1);;
+
+
+(* A few tests to check the function works correctly *)
+
+assert ((bubble_sort []) = []);;
+assert ((bubble_sort [1]) = [1]);;
+
+assert ((bubble_sort [2; 1]) = [1; 2]);;
+
+assert ((bubble_sort [-1; 4]) = [-1; 4]);;
+
+assert ((bubble_sort [3; 2; 1]) = [1; 2; 3]);;  
+assert ((bubble_sort [1; 2; 3]) = [1; 2; 3]);;
+
+assert ((bubble_sort [3; 2; 1; 4]) = [1; 2; 3; 4]);;  
+assert ((bubble_sort [1; 2; 3; 4]) = [1; 2; 3; 4]);;
+
+assert ((bubble_sort [10; 40; 3; 2;]) = [2; 3; 10; 40]);;
+
+assert ((bubble_sort [10; 40; 3; 2; 4050; -6; 28; 32;]) = [-6; 2; 3; 10; 28; 32; 40; 4050]);;
+