Initial data commit

Task/Sorting-algorithms-Cocktail-sort-with-shifting-bounds/Go/sorting-algorithms-cocktail-sort-with-shifting-bounds.go

@@ -0,0 +1,104 @@
+package main
+
+import (
+    "fmt"
+    "math/rand"
+    "time"
+)
+
+// translation of pseudo-code
+func cocktailShakerSort(a []int) {
+    var begin = 0
+    var end = len(a) - 2
+    for begin <= end {
+        newBegin := end
+        newEnd := begin
+        for i := begin; i <= end; i++ {
+            if a[i] > a[i+1] {
+                a[i+1], a[i] = a[i], a[i+1]
+                newEnd = i
+            }
+        }
+        end = newEnd - 1
+        for i := end; i >= begin; i-- {
+            if a[i] > a[i+1] {
+                a[i+1], a[i] = a[i], a[i+1]
+                newBegin = i
+            }
+        }
+        begin = newBegin + 1
+    }
+}
+
+// from the RC Cocktail sort task (no optimizations)
+func cocktailSort(a []int) {
+    last := len(a) - 1
+    for {
+        swapped := false
+        for i := 0; i < last; i++ {
+            if a[i] > a[i+1] {
+                a[i], a[i+1] = a[i+1], a[i]
+                swapped = true
+            }
+        }
+        if !swapped {
+            return
+        }
+        swapped = false
+        for i := last - 1; i >= 0; i-- {
+            if a[i] > a[i+1] {
+                a[i], a[i+1] = a[i+1], a[i]
+                swapped = true
+            }
+        }
+        if !swapped {
+            return
+        }
+    }
+}
+
+func main() {
+    // First make sure the routines are working correctly.
+    a := []int{21, 4, -9, 62, -7, 107, -62, 4, 0, -170}
+    fmt.Println("Original array:", a)
+    b := make([]int, len(a))
+    copy(b, a) // as sorts mutate array in place
+    cocktailSort(a)
+    fmt.Println("Cocktail sort :", a)
+    cocktailShakerSort(b)
+    fmt.Println("C/Shaker sort :", b)
+
+    // timing comparison code
+    rand.Seed(time.Now().UnixNano())
+    fmt.Println("\nRelative speed of the two sorts")
+    fmt.Println("  N    x faster (CSS v CS)")
+    fmt.Println("-----  -------------------")
+    const runs = 10 // average over 10 runs say
+    for _, n := range []int{1000, 2000, 4000, 8000, 10000, 20000} {
+        sum := 0.0
+        for i := 1; i <= runs; i++ {
+            // get 'n' random numbers in range [0, 100,000]
+            // with every other number being negated
+            nums := make([]int, n)
+            for i := 0; i < n; i++ {
+                rn := rand.Intn(100000)
+                if i%2 == 1 {
+                    rn = -rn
+                }
+                nums[i] = rn
+            }
+            // copy the array
+            nums2 := make([]int, n)
+            copy(nums2, nums)
+
+            start := time.Now()
+            cocktailSort(nums)
+            elapsed := time.Since(start)
+            start2 := time.Now()
+            cocktailShakerSort(nums2)
+            elapsed2 := time.Since(start2)
+            sum += float64(elapsed) / float64(elapsed2)
+        }
+        fmt.Printf(" %2dk      %0.3f\n", n/1000, sum/runs)
+    }
+}