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import java.util.Scanner;

/**

* Implementation of QuickSort

*

* @author Unknown

*

*/

public class Quicksort{

/**

* The main method

*

* @param args Command line arguments

*/

public static void main(String[] args){

Scanner input = new Scanner(System.in);

int[] array;

int size = 0;

//Prompt user to create array and its elements

System.out.print("Enter the size of the array: ");

size = input.nextInt();

array = new int[size];

for (int i = 0; i < size; i++){

System.out.print("For index " + i + ", give an integer input: ");

array[i] = input.nextInt();

}

//Output inputted array

System.out.println("The array is: ");

printarray(array);

System.out.println();

//Run quicksort, and output sorted array

quicksort(array, 0, array.length - 1);

System.out.println("The sorted array is: ");

printarray(array);

System.out.println();

input.close();

}

/**

* QuickSort method

*

* @param ar Array to perform QuickSort

* @param start Start of the array

* @param end End of the array

*/

public static void quicksort(int[] ar, int start, int end){

int[] array;

int i = start, j = end;

if (end-start >= 1){

int pivot = ar[end];

while (i< j){

while (ar[i]<pivot && i<end){

i++;

}

while (ar[j]>=pivot && j>start){

j--;

}

if (i<j){

swap(ar, i, j);

}

} swap(ar, end, i);

quicksort(ar, start, i-1);

quicksort(ar, i+1, end);

} else{

return;

}

}

/**

* Helper Method 1 - Swaps elements of an array

*

* @param ar Array to be used

* @param index1 Index 1 to be switched with Index 2

* @param index2 Index 2 to be switched with Index 1

*/

public static void swap(int[] ar, int index1, int index2){

int temp = ar[index1];

ar[index1] = ar[index2];

ar[index2] = temp;

}

/**

* Helper Method 2 - Prints the elements of an array

*

* @param array Array to be printed

*/

public static void printarray(int[] array){

for (int data : array){

System.out.print(data + " ");

}

}

}