QUICK SORT

/* quick sort*/

#include<stdio.h>

int a[20],n;

void sort(int a[],int lb,int ub)

{

          int p;

          if(lb>=ub)

                   return;

          p=partetion(a,lb,ub);

          sort(a,lb,p-1);

          sort(a,p+1,ub);

}

int partetion(int a[],int lb,int ub)

{

          int down,up,key,t;

          down=lb;

          up=ub;

          key=a[lb];

          while(down<up)

          {

                   while((key>=a[down]) &&(down<up))

                             down++;

                   while(key<a[up])

                             up--;

                   if(down<up)

                   {

                             t=a[down];

                             a[down]=a[up];

                             a[up]=t;

                   }

          }

          a[lb]=a[up];

          a[up]=key;

          return up;

}

main()

{

          int i;

          printf("enter the number of elements:");

          scanf("%d",&n);

          for(i=1;i<=n;i++)

          {

                   printf("enter element %d:",i);

                   scanf("%d",&a[i]);

          }

          printf("unsorted list:");

          for(i=1;i<=n;i++)

                   printf("\t%d",a[i]);

          sort(a,1,n);

          printf("\nsorted list:\n");

          for(i=1;i<=n;i++)

                   printf("%d\t",a[i]);

}

                   .......OUTPUT.......

enter the number of elements:5

enter element 1:6

enter element 2:9

enter element 3:3

enter element 4:1

enter element 5:7

unsorted list:  6       9       3       1       7

sorted list:

1       3       6       7       9