golang about 04_quicksort (#43)

* recursion_Golang

* go_fmt

* selection_sort_Golang

* rm-golang

* selection_sort_Golang

* selection_sort_Golang

* selection_sort_Golang

* dynamic_golang

* golang 05_hash_tables 02_check_voter.go

* golang 05_hash_tables 01_price_of_groceries

* add 01_loop_sum in 04_quicksort

* 02_recursive_sum in 04_quicksort

* 03_recursive_count in 04_quicksort

* 04_recursive_max in 04_quicksort

* 05_quicksort in 04_quicksort

04_quicksort/golang/01_loop_sum.go

@@ -0,0 +1,15 @@
+package main
+
+import "fmt"
+
+func sum(arr []int) int {
+	total := 0
+	for _, num := range arr {
+		total += num
+	}
+	return total
+}
+
+func main() {
+	fmt.Println(sum([]int{1, 2, 3, 4}))
+}

04_quicksort/golang/02_Recursive_sum.go

@@ -0,0 +1,14 @@
+package main
+
+import "fmt"
+
+func sum(arr []int) int {
+	if len(arr) == 0 {
+		return 0
+	}
+	return arr[0] + sum(arr[1:])
+}
+
+func main() {
+	fmt.Println(sum([]int{1, 2, 3, 4}))
+}

04_quicksort/golang/03_recursive_count.go

@@ -0,0 +1,14 @@
+package main
+
+import "fmt"
+
+func count(list []int) int {
+	if len(list) == 0 {
+		return 0
+	}
+	return 1 + count(list[1:])
+}
+
+func main() {
+	fmt.Println(count([]int{0, 1, 2, 3, 4, 5}))
+}

04_quicksort/golang/04_recursive_max.go

@@ -0,0 +1,22 @@
+package main
+
+import "fmt"
+
+func max(list []int) int {
+	if len(list) == 2 {
+		if list[0] > list[1] {
+			return list[0]
+		}
+		return list[1]
+	}
+
+	subMax := max(list[1:])
+	if list[0] > subMax {
+		return list[0]
+	}
+	return subMax
+}
+
+func main() {
+	fmt.Println(max([]int{1, 5, 10, 25, 16, 1}))
+}

04_quicksort/golang/05_quicksort.go

@@ -0,0 +1,29 @@
+package main
+
+import "fmt"
+
+func quicksort(list []int) []int {
+	if len(list) < 2 {
+		return list
+	} else {
+		pivot := list[0]
+
+		var less = []int{}
+		var greater = []int{}
+		for _, num := range list[1:] {
+			if pivot > num {
+				less = append(less, num)
+			} else {
+				greater = append(greater, num)
+			}
+		}
+
+		less = append(quicksort(less), pivot)
+		greater = quicksort(greater)
+		return append(less, greater...)
+	}
+}
+
+func main() {
+	fmt.Println(quicksort([]int{10, 5, 2, 3}))
+}