add: slice internals backing array and slice header

16-slices/exercises/17-internals-backing-array-sort/main.go

@@ -0,0 +1,52 @@
+// For more tutorials: https://blog.learngoprogramming.com
+//
+// Copyright © 2018 Inanc Gumus
+// Learn Go Programming Course
+// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
+//
+
+package main
+
+import (
+	"fmt"
+)
+
+// ---------------------------------------------------------
+// EXERCISE: Sort the backing array
+//
+//  1. Sort only the middle 3 items.
+//
+//  2. All the slices should see your change.
+//
+//
+// RESTRICTION
+//
+//  Do not sort manually. Sort by slicing then by using the sort package.
+//
+//
+// EXPECTED OUTPUT
+//
+//  Original: [pacman mario tetris doom galaga frogger asteroids simcity metroid defender rayman tempest ultima]
+//
+// Sorted  : [pacman mario tetris doom galaga asteroids frogger simcity metroid defender rayman tempest ultima]
+//
+//
+// HINT:
+//
+//   Middle items are         : [frogger asteroids simcity]
+//
+//   After sorting they become: [asteroids frogger simcity]
+//
+// ---------------------------------------------------------
+
+func main() {
+	items := []string{
+		"pacman", "mario", "tetris", "doom", "galaga", "frogger",
+		"asteroids", "simcity", "metroid", "defender", "rayman",
+		"tempest", "ultima",
+	}
+
+	fmt.Println("Original:", items)
+	fmt.Println()
+	fmt.Println("Sorted  :", items)
+}

16-slices/exercises/17-internals-backing-array-sort/solution/main.go

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+// For more tutorials: https://blog.learngoprogramming.com
+//
+// Copyright © 2018 Inanc Gumus
+// Learn Go Programming Course
+// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
+//
+
+package main
+
+import (
+	"fmt"
+	"sort"
+)
+
+func main() {
+	items := []string{
+		"pacman", "mario", "tetris", "doom", "galaga", "frogger",
+		"asteroids", "simcity", "metroid", "defender", "rayman",
+		"tempest", "ultima",
+	}
+
+	fmt.Println("Original:", items)
+
+	mid := len(items) / 2
+	smid := items[mid-1 : mid+2]
+
+	// sorting the smid will affect the items
+	// as well. their backing array is the same.
+	sort.Strings(smid)
+
+	fmt.Println()
+	fmt.Println("Sorted  :", items)
+}