QuickSort is an in-place sorting algorithm with worst-case time complexity of
​​QuickSort can be implemented iteratively and recursively. We’ll mainly focus on the recursive implementation, as it is far more convenient, intuitive and simplistic. Iterative implementation is generally unrecommended. Arrays are used as an example here, but it can be implemented on other data structures (like linked lists) as well.
The algorithm can be broken down into 3 parts.
In the above illustration, we used the first element of the ​array as a pivot (though any of the elements can be taken).
import java.util.*;class Quick_Sort {public static int[] QuickSort(int[] arr, int elements) {if(elements < 2){ //Base Casereturn arr;}int current_position=0; //position of pivot elementint temp; //a temporary variable to assist in swappingfor(int i=1; i<elements; i++) //Partitioning loop{if(arr[i] <= arr[0]){current_position++;temp = arr[i];arr[i] = arr[current_position];arr[current_position] = temp;}}temp = arr[0];arr[0] = arr[current_position];arr[current_position] = temp; //Brings pivot to it's appropriate positionint[] left = QuickSort(arr,current_position); //sorts the elements to the left of pivotint[] arr2 = Arrays.copyOfRange(arr, current_position+1, elements);//separates elements right of pivotint[] right = QuickSort(arr2, elements-current_position-1); //sorts the elements to the right of pivotint[] final_array = new int[elements]; //final array, to merge everything togetherfor(int i=0; i<current_position; i++){final_array[i] = left[i];}final_array[current_position] = arr[current_position];for(int i=current_position+1; i<elements; i++){final_array[i] = right[i-current_position-1];}return final_array;}public static void main( String args[] ) {int[] array = {4,2,7,3,1,6}; //array to be sortedSystem.out.print("Original Array: [");for(int i=0; i<array.length;i++){System.out.print(array[i]);System.out.print(" ");}System.out.println("]");array = QuickSort(array, array.length);//sortingSystem.out.print("Sorted Array: ["); //printing the sorted arrayfor(int i=0; i<array.length;i++){System.out.print(array[i]);System.out.print(" ");}System.out.print("]");}}