[tech] xor list

XOR list example

#include <stdio.h>

#include <stdlib.h>

#include <assert.h>

struct xnode {

 int data;

 unsigned long direction;

};

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

void walk_list(struct xnode *list);

http://www.c.happycodings.com/Data_Structures/code31.html

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");

}