/* Program to demonstrate Randomized quick sort (recursive) */

#include  <stdio.h>
#include  <stdlib.h>
#include  <conio.h>

void  quick(int  x[], int  lb, int  ub) ;
int  partition(int  x[], int  lb, int  ub) ;
void  show(int  x[], int  lb, int  ub) ;

void  main()
{
    int  i, n, x[20] ;
    clrscr() ;
    printf("Enter the number of elements: ") ;
    scanf("%d",&n) ;
    printf("Enter the elements:\n") ;
    for(i=0; i<n; i++)
        scanf("%d",&x[i]) ;
    quick(x,0,n-1) ;
    printf("Sorted array is as shown:\n") ;
    for(i=0; i<n; i++)
        printf("%d ",x[i]) ;
    getch() ;
}

void  quick(int  x[], int  lb, int  ub)
{
    int   j, k, temp ;
    if(lb<ub)
        {
            k=rand()%(ub-lb+1) + lb ;
            temp=x[k] ;
            x[k]=x[lb] ;
            x[lb]=temp ;
            j=partition(x,lb,ub) ;
            quick(x,lb,j-1) ;
            quick(x,j+1,ub) ;
        }
}

int  partition(int  x[], int  lb, int  ub)
{
    int  a, down, up, temp ;
    a=x[lb] ;
    up=ub ;
    down=lb ;
    while(down<up)
        {
            while(x[down]<=a&&down<ub)
                down++ ;
            while(x[up]>a)
                up-- ;
            if(down<up)
                {
                    temp=x[down] ;
                    x[down]=x[up] ;
                    x[up]=temp ;
                }
        }
    x[lb]=x[up] ;
    x[up]=a ;
    show(x,lb,ub) ;
    return  up ;
}

void  show(int  x[], int  lb, int  ub)
{
    int  i ;
    for(i=lb ; i<=ub ; i++)
        printf("%d ",x[i]) ;
    printf("\n\n") ;
}

/* The method show() is optional. It is written to show output of each pass. It may not be written in theory exam. It is required only in practical exams */