Quick Sort, as the name indicate, sorts any list of data very quickly. Quick sort very fast data sorting technique and it requires very less additional space. It is based on the rule of Divide and Conquer(also called partition-exchange sort). http://www.tutorial4us.com/data-structure/c-quick-sort

1. /*** program of quick sort ****
* http://www.tutorial4us.com/data-structure/c-quick-sort */
#include<stdio.h>
#include<conio.h>
void quicksort(int [],int,int);
int partition(int [],int,int);
main()
{
int a[20],p,q,i,n;
clrscr();
printf("How many elements you want to enter: ");
scanf("%d",&n);
for(i=0; i<n; i++)
{
printf("nEnter any %d elements: "n);
scanf("%d",&a[i]);
}
p=0;
q=n-1;

2. printf("nnnArray Befor Sorting : ");
for(i=0; i<n; i++)
{
delay(500);
printf("%5d",a[i]);
}
quicksort(a,p,q);
printf("nnnArray After Sorting : ");
for(i=0; i<n; i++)
{
delay(500);
printf("%5d",a[i]);
}
getch();
return 0;
}
void quicksort(int a[],int p,int q)
{
int j;
if(p<q)
{
j=partition(a,p,q+1);

3. quicksort(a,p,j-1);
quicksort(a,j+1,q);
}
}
int partition(int a[],int m,int p)
{
int v,i,j;
int temp;
v=a[m];
i=m;j=p;
do
{
do
{
i += 1;
}
while(a[i]<v);
do
{
j -= 1;
}
while(a[j]>v);
if(i<j)

4. {
temp = a[i];
a[i] = a[j];
a[j] = temp;
}
}
while(i<j);
a[m] =a[j];
a[j] = v;
return j;
}