2 way List

I have a list, having nodes with only int an a pointer to the next node.
I want to make my list 2 way (meaning that i need to add one more pointer to the previous node).
This is my try for one way

Code:

struct AkeraiosStruct {
           int Value;
           AkeraiosStruct * next;
} AkeraiosStruct;

void insert_at_end (AkeraiosStruct * * ptraddr, int v)
                       /* Insert v as last element of list *ptraddr */
                       
{ 
    AkeraiosStruct * templist;
    templist = * ptraddr;
    while (*ptraddr != NULL)                     /* Go to end of list */
    ptraddr = &((*ptraddr)->next);/* Prepare what we need to change */
    *ptraddr = malloc(sizeof(struct AkeraiosStruct)); /* Space for new node */
    (*ptraddr)->Value = v;                               /* Put value */ 
    (*ptraddr)->next = NULL;              /* There is no next element */
}


void insert_at_start(AkeraiosStruct * *ptraddr, int v)
                      /* Insert v as first element of list *ptraddr */
{ AkeraiosStruct * templist;
  templist = *ptraddr;                /* Save current start of list */
  *ptraddr = malloc(sizeof(struct AkeraiosStruct)); /* Space for new node */
  (*ptraddr)->Value = v;                               /* Put value */
  (*ptraddr)->next = templist;      /* Next element is former first */
  
}

And this is my try for two way list

Code:

struct AkeraiosStruct {
           int Value;
           AkeraiosStruct * next;
           AkeraiosStruct * prev;
} AkeraiosStruct;

But i can't modify insert_at_start/end in order to add the prev pointer.

Originally Posted by ch4

But i can't modify insert_at_start/end in order to add the prev pointer.

So how do you expect to do this if you can't edit the code?

I do edit my code but it fails

Code:

void insert_at_end (AkeraiosStruct * * ptraddr, int v)
                       /* Insert v as last element of list *ptraddr */
                       
{ 
    AkeraiosStruct * templist;
    AkeraiosStruct * templist_prv;
    templist = * ptraddr;
    
    while (*ptraddr != NULL)                     /* Go to end of list */
    ptraddr = &((*ptraddr)->next);/* Prepare what we need to change */


    templist_prv=&((*ptrddr);  

    *ptraddr = malloc(sizeof(struct AkeraiosStruct)); /* Space for new node */
    
    (*ptraddr)->Value = v;                               /* Put value */ 

    (*ptraddr)->next = NULL;              /* There is no next element */
}

void insert_at_start(AkeraiosStruct * *ptraddr, int v)
                      /* Insert v as first element of list *ptraddr */
{ AkeraiosStruct * templist;
   AkeraiosStruct * templist_prv;
  templist_prv=(*ptraddr)->prev;  /*Save current prev node*/
  templist = *ptraddr;                /* Save current start of list */
  *ptraddr = malloc(sizeof(struct AkeraiosStruct)); /* Space for new node */
  (*ptraddr)->Value = v;                               /* Put value */
  (*ptraddr)->prev=templist_prv;
  (*ptraddr)->next = templist;      /* Next element is former first */
  
}