XOR list example

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

struct xnode
{
int data;
unsigned long direction;
};

struct xnode *add_data(int data, struct xnode* list);
void walk_list(struct xnode *list);

int main(void)
{

struct xnode *l2 = add_data(2, NULL);
struct xnode *l1 = add_data(1, l2);
struct xnode *l3 = add_data(3, l2);
struct xnode *l4 = add_data(4, l3);

printf("front -> back....\n");
walk_list(l1);
printf("back -> front....\n");
walk_list(l4);

return 0;
}

struct xnode *add_data(int data, struct xnode *list)
{
struct xnode *newxnode = malloc(sizeof(struct xnode));

assert(newxnode);
newxnode->direction = (unsigned long)list;
newxnode->data = data;

if(list != NULL)
list->direction ^= (unsigned long)newxnode;

return newxnode;
}

void walk_list(struct xnode *list)
{
unsigned long prev = 0;

while(list != NULL) {
unsigned long next = prev ^ list->direction;
printf("%d ", list->data);
prev = (unsigned long)list;
list = (struct xnode *)next;
}

printf("\n");
}