C Program for Quick Sorting - Quick Sort Program in to Sort Numbers

Quick sort is one of the most efficient sorting algorithms. Here i post a C program to implement Quick sorting. This program is to sort given numbers is ascending order. To sort in descending order using quick sort, only slight changes are needed in program. Changes needed for sorting in descending order are marked in the program as comments.

#include<stdio.h>
void quicksort(int [10],int,int);
int main()
  {
  int x[20],size,i;
  printf("Enter size of the array: ");
  scanf("%d",&size);
  printf("Enter %d elements: ",size);
  for(i=0;i<size;i++)
     scanf("%d",&x[i]);
  quicksort(x,0,size-1);
  printf("Sorted elements: ");
  for(i=0;i<size;i++)
     printf(" %d",x[i]);
  return 0;
  }

void quicksort(int x[10],int first,int last)
  {
  int pivot,j,temp,i;
  if(first<last)
     {
     pivot=first;
     i=first;
     j=last;
     while(i<j)
        {
        while(x[i]<=x[pivot]&&i<last)//for descending, use >= instead of <=
            i++;
        while(x[j]>x[pivot])//for descending, use < instead of >=
            j--;
        if(i<j)
            {
            temp=x[i];
            x[i]=x[j];
            x[j]=temp;
            }
        }
    temp=x[pivot];
    x[pivot]=x[j];
    x[j]=temp;
    quicksort(x,first,j-1);
    quicksort(x,j+1,last);
}
}

Output:
Enter size of the array: 5

Enter 5 elements:
3
8
0
1
2
Sorted elements: 0 1 2 3 8