Easy Quick Sort

quicksort.go

package main

import (
	"fmt"

	"gitlab.com/NebulousLabs/fastrand"
)

func main() {
	slice := generateIntSlice(20)
	fmt.Printf("Unsorted Slice:\n%v\n", slice)
	fmt.Printf("Sorted Slice:\n%v\n", quickSort(slice))
}

// generateIntSlice creates a random int slice of the input size using the
// fastrand package Intn
func generateIntSlice(size int) []int {
	// Initialize int slice, size and capacity
	slice := make([]int, size, size)

	// create random slice
	for i := 0; i < size; i++ {
		slice[i] = fastrand.Intn(200)
	}
	return slice
}

// quickSort sorts a slice in place using a pivot element
func quickSort(arr []int) []int {
	if len(arr) <= 1 {
		return arr
	}

	// Set the first element as the pivot
	pivot := arr[0]
	var smaller, larger []int
	for i := 1; i < len(arr); i++ {
		if arr[i] < pivot {
			smaller = append(smaller, arr[i])
		} else {
			larger = append(larger, arr[i])
		}
	}

	// Call quicksort on two halves
	smallerSorted := quickSort(smaller)
	largerSorted := quickSort(larger)

	return append(append(smallerSorted, pivot), largerSorted...)
}