Does this code I wrote do what we expect from the quick sort algorithm?

Question

package labodeva;
import java.util.Scanner;
public class odev5dene {
static int[] quick(int kucuk,int buyuk,int[] arr,int pivot) {
 int bos[] = new int[100];
 int t=0;
 while(kucuk<=buyuk) { // buyuk is big kucuk is small
 if(arr[kucuk]<=arr[pivot]) {
 kucuk++;
 }
 else if(arr[buyuk]>arr[pivot]) {
 buyuk--;
 }
 else{
 bos[0] = arr[kucuk];
 arr[kucuk]=arr[buyuk];
 arr[buyuk] = bos[0];
 buyuk--;
 kucuk++;
 }
 }
 if(kucuk>buyuk) {
 bos[0] = arr[pivot];
 arr[pivot]=arr[buyuk];
 arr[buyuk]=bos[0];
 pivot=buyuk; //sil
 }
 if(pivot-1>0&&pivot+1<arr.length) {
 quick(0,pivot-1,arr,0);
 quick(pivot+1,arr.length-1,arr,pivot+1);
 }
 if(pivot+1<arr.length&&pivot-1<0) {
 quick(pivot+1,arr.length-1,arr,pivot+1);
 }
 return arr;
}
 public static void main(String[] args) {
 int a =0;
 Scanner scan = new Scanner(System.in);
 System.out.println("Please enter how many value do you want to add the array : ");
 a=scan.nextInt();
 int k[] =new int[a]; 
 for(int i=0;i<a;i++) {
 System.out.println("Please enter your "+(i+1)+".value");
 k[i]=scan.nextInt();
 }
 k=quick(0,a-1,k,0); // it starts 0. element as pivot and goes on and also small and equal number value starts here big number value starts at the end of list
 for(int i=0;i<a;i++) {
 System.out.println(k[i]);
 }
 }
}

i wrote this code and it sorts the given array but i tried to do quicksort is this quicksort i am not sure can you check ?

• greybeard: (I always found it slightly more taxing to follow source code with comments&identifiers in my first language, and keywords in English as compared to sticking to (Pidgin) English.)
• greybeard: I expect a production strength quicksort implementation to a) use additional space growing not nearly as fast as the number n of items even worst case b) not show worst case time for reverse sorted input, let alone sorted one.

Answer 1

1. In quicksort, when you are sorting from elements 20 to 40, and the split becomes 30, the recursive calls should be to sort 20 to 29 and 31 to 40. You did 0 to 29 and 31 to max. I suspect this made your code degenerate into an \$O(n^2)\$ sort (but still work).
2. In quicksort, you should not pass in a pivot. The function should work that out itself.
3. Variable bos is a problem. You only ever use bos[0], so you shouldn't even make an array, just a simple variable.