C Program for Binary Search and Towers of Hanoi using Recursion

C Program for Binary Search and Towers of Hanoi using Recursion.
Source: Dr. G T Raju, Professor & Head, Dept. of CSE, RNSIT

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main()
{
    int n,a[50],key,opn,i,pos;
    do
    {
        clrscr();
        printf(" \n\n Press 1 -> Binary Search , 2-> Towers of Hanoi 3-> Quit\n");
        scanf("%d",&opn);
        switch(opn)
        {
        case 1: printf(" How Many Elements?");
            scanf("%d",&n);
            printf(" Read all the elements is ASC order \n");
            for(i=1;i<=n;i++)
                scanf("%d",&a[i]);
            printf(" Read the Key Element\n");
            scanf("%d",&key);
            pos=BS(a,key,1,n);
            if(pos)	 printf(" Success: %d found at %d \n", key,pos);
            else	 printf(" Falure: %d Not found in the list ! \n",key);
            break;
        case 2: printf("\n\n How Many Disks ?");
            scanf("%d", &n);
            printf("\n\n Result of Towers of Hanoi for %d Disks \n",n);
            tower(n,'A','B','C');
            printf("\n\n Note: A-> Source, B-> Intermediate, C-> Destination\n");
            break;
        case 3: printf(" Terminating \n"); break;
        default: printf(" Invalid Option !! Try Again !! \n");
        }
        printf(" Press a Key. . . ");  getch();
    }while(opn != 3);
}
int BS(int a[], int key,int low,int high)
{
    int mid;
    if(low > high) return 0; /* failure */
    else
    {
        mid=(low+high)/2;
        if(a[mid]== key) return mid; /* Success */
        if(key < a[mid]) return(BS(a,key,low,mid-1));
        return(BS(a,key,mid+1,high));
    }
}
tower(int n, char src, char intr, char dst)
{
    if(n > 0)
    {
        tower(n-1,src,dst,intr);
        printf("Move disk %d from %c to %c \n", n,src,dst);
        tower(n-1,intr,src,dst);
    }
}

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