feat: Add Cocktail Sort (#660)

* add cocktail sort

* add test for cocktail sort

* change comments

* add comments on cocktailsort.go

* add start and end vars to cocktailsort.go for optimization

* fix: change for loop structure

* fix: change constraints from integer to ordered on cocktailsort.go

* test: add benchmark for cocktailsort

---------

Co-authored-by: Rak Laptudirm <[email protected]>

Author: migueldalberto

Diff for: sort/cocktailsort.go

@@ -0,0 +1,54 @@
+// Implementation of Cocktail sorting
+// reference: https://en.wikipedia.org/wiki/Cocktail_shaker_sort
+
+package sort
+
+import "github.com/TheAlgorithms/Go/constraints"
+
+// Cocktail sort is a variation of bubble sort, operating in two directions (beginning to end, end to beginning)
+func Cocktail[T constraints.Ordered](arr []T) []T {
+	if len(arr) == 0 { // ignore 0 length arrays
+		return arr
+	}
+
+	swapped := true // true if swapped two or more elements in the last loop
+	// if it loops through the array without swapping, the array is sorted
+
+	// start and end indexes, this will be updated excluding already sorted elements
+	start := 0
+	end := len(arr) - 1
+
+	for swapped {
+		swapped = false
+		var new_start int
+		var new_end int
+
+		for i := start; i < end; i++ { // first loop, from start to end
+			if arr[i] > arr[i+1] { // if current and next elements are unordered
+				arr[i], arr[i+1] = arr[i+1], arr[i] // swap two elements
+				new_end = i
+				swapped = true
+			}
+		}
+
+		end = new_end
+
+		if !swapped { // early exit, skipping the second loop
+			break
+		}
+
+		swapped = false
+
+		for i := end; i > start; i-- { // second loop, from end to start
+			if arr[i] < arr[i-1] { // same process of the first loop, now going 'backwards'
+				arr[i], arr[i-1] = arr[i-1], arr[i]
+				new_start = i
+				swapped = true
+			}
+		}
+
+		start = new_start
+	}
+
+	return arr
+}

Diff for: sort/sorts_test.go

@@ -1,11 +1,12 @@
 package sort_test
 
 import (
-	"github.com/TheAlgorithms/Go/sort"
 	"math/rand"
 	"reflect"
 	"testing"
 	"time"
+
+	"github.com/TheAlgorithms/Go/sort"
 )
 
 func testFramework(t *testing.T, sortingFunction func([]int) []int) {
@@ -85,6 +86,10 @@ func TestBucketSort(t *testing.T) {
 	testFramework(t, sort.Bucket[int])
 }
 
+func TestCocktailSort(t *testing.T) {
+	testFramework(t, sort.Cocktail[int])
+}
+
 func TestExchange(t *testing.T) {
 	testFramework(t, sort.Exchange[int])
 }
@@ -222,6 +227,10 @@ func BenchmarkBucketSort(b *testing.B) {
 	benchmarkFramework(b, sort.Bucket[int])
 }
 
+func BenchmarkCocktailSort(b *testing.B) {
+	benchmarkFramework(b, sort.Cocktail[int])
+}
+
 func BenchmarkExchange(b *testing.B) {
 	benchmarkFramework(b, sort.Exchange[int])
 }