Thread: Tower Of Hanoi

Use the search, Luke!

Quzah.

Are you asking me, or the original poster? Yes, I can do it.

Quzah.

Haven't tested it, but i think this'll work:

Code:

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

/* The 'class'. */
struct cell {
	int disc;
	struct cell *next;
};

/* The initializer for 'cell'. */
struct cell *newCell( int d )
{
    struct cell *c = malloc( sizeof( struct cell ) );
    c->disc = d;
    c->next = NULL;
	return c;
}

/* The 'list' class. */
struct list {
	struct cell *rear;
};

/**
*** Their implementation of 'empty()' appears to be done incorrectly.
*** IMO, a null list would crash their application.
**/
int empty( struct list *l ) { return rear == NULL; }

/* The 'pop' function. */
int *pop( struct list * l )
{
    struct cell *c = NULL;
    int d = -1;

    if( !l ) { perror( "'pop( )' passed NULL list'" ); exit( 0 ); }

    if( l->rear )
	{
		c = l->rear;
		l->rear = l->rear->next;
		d = c->disc;
		free( c );
	}
	return d;
}

/* The 'push' function. */
void push(int d, struct list *l ) 
{ 
	struct cell *c;
	c = newCell( d );
    c->next = l->rear;
    l->rear = c;
} 

void freeList( struct list *l ) { while( !empty( l ) ) pop( l ); }

typedef int (*oper)(int); 

int decr(int a) 
{ 
a--; 
if(a<0) 
a=2; 
return a; 
} 

int incr(int a) 
{ 
a = (a+1)%3; 
return a; 
} 

int main(void) 
{
	struct list pegs[3];

	int n, curr, p1=1, p2=2, d0,d1,d2, i;
	oper incr_decr;

	printf("Enter the number of discs: ");
    scanf( "%d", &n );

	for( i = n; i > 0; i-- )
        push( i, pegs[curr] );

	incr_decr = n%2 ? decr : incr; 
	while(1)
	{
		d0 = pop( pegs[curr] );
		printf("Disc %d from %d ", d0, curr );

		curr = incr_decr(curr); 
		printf("to %d.\n", curr );

		p1 = incr_decr(p1); 
		p2 = incr_decr(p2); 

		if(!empry(pegs[p1]) && !empty(pegs[p2])) 
		{ 
			d1 = pop( pegs[p1] );
			d2 = pop( pegs[p2] );

			if(d1 < d2) 
			{ 
				push( d2, pegs[p2] );
				push( d1, pegs[p2] );
				printf("Disc %d from %d to %d.\n", d1, p1, p2 );
			}
			else 
			{
				push( d1, pegs[p1] );
				push( d2, pegs[p1] );
				printf("Disc %d from %d to %d.\n", d2, p2, p1 );
			}
		} 
		else 
		{ 
			if( empty( pegs[p1] ) && empty( pegs[p2] ) ) 
				break; 
			if( empty( pegs[p1] ) ) 
			{ 
				d2 = pop( pegs[p2] ); 
				d1 = pop( pegs[p1] ); 
				printf("Disc %d from %d to %d.\n", d2, p2, p1 );
			} 
			else 
			{
				d1 = pop( pegs[p1] );
				push( d1, pegs[p2] );
				printf("Disc %d from %d to %d.\n", d1, p1, p2 ); 
			} 
		} 
	} 
	return 1;
}

Quzah.

'rear' is declared in 'list'. Thus, every instance of 'list' has a member named 'rear'. Additionally, pop is also correct. Pop is also correct. (glancing at the code now) In each case, the function should work correctly. Perhaps I didn't call them correctly. The only thing I can think of is perhaps:

push( thisNumber, &pegs[curr] );

Anyway, those functions are designed correctly and they should work if called correctly. Pass them a list and they'll pop a node from it or, or push one on it. Shrug. I donno, I'm tired and work is almost done for the day.

Quzah.