Question

I have a linked list, and I want to sort them by names
(for example the names “Bx”, “Tx”, “Ax” would become : “Ax”, “Bx”, “Tx”)…
I need to switch the names if the one in the node’s right has a “smaller name”..

this is what I wrote:

typedef struct data
{
char *name;
}data;

typedef struct Node 
{
data NodeData;
struct Node *next;
struct Node *prev;
}Node;

void Sorting(Node *head)
{
 Node *temp = head;
 Node *temp2 = (Node*)malloc(sizeof(Node));
 while (temp != NULL)
 {
       if (1 == (strcmp(temp -> NodeData.name, temp -> next -> NodeData.name))) 
       {
              strcpy (temp2 -> NodeData.name, temp -> NodeData.name);
              strcpy (temp -> NodeData.name, temp -> next -> NodeData.name);
              strcpy (temp -> next -> NodeData.name, temp2 -> NodeData.name);
       } 

       temp = temp -> next;

 }

}

I’m getting an runtime – error on the part where I need to swarp betwen the node’s name(the strcpy lines):
An access violation (segmentation fault)…

Answer 1

if (1 == (strcmp(temp -> NodeData.name, temp -> next -> NodeData.name))) {...}

When this line is executed, there is no guarantee that temp->next is not NULL.
If it is NULL, temp->next->NodeData.Name would be rather painfull.

Also, as has been said, testing strcmp()s result against 1 is not right. strcmp can resutning any value equal to zero, < zero or > zero.

Also, as has been said, strcpy() is not right; the strings could have different allocated sizes, or could live in non-writable memory (string constants) . Swapping the pointers will suffice.

UPDATE:

void Sorting(Node *head)
{
 Node *temp ;

                /* since the compare dereferences temp->next you'll have to verify that it is not NULL */
 for (temp = head; temp && temp->next; temp = temp->next)  
 {
       if (strcmp(temp->NodeData.name, temp->next->NodeData.name) > 0 )  
       {
                /* no need for a whole node, since you only copy a pointer */
              char *cp;
              cp = temp->NodeData.name;
              temp->NodeData.name = temp->next->NodeData.name;
              temp->next->NodeData.name = cp;
       } 

 }

}

BTW: bubble sorting a linked list is really ugly. Linked lists are easyer and more elagantly sorted by mergesort.