Thread: Inserting to sorted linked list

Code:

         else if ( strcmp( node->name, iter->name ) < 0){
            node->nextProduct = iter->nextProduct;
            iter->nextProduct = node;
            break;
         }
         iter = iter->nextProduct;

Your problem is in the comparison. Since you want to add node's after the iter, you have to insert when node->name should appear after iter->name.

That's a pretty simple fix huh?

After I fixed it I got a nice sorted list:

Code:

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

#define PRODUCT_NAME_MAX 100
#define PRODUCT_BRAND_MAX (PRODUCT_NAME_MAX)

typedef struct productNode
{
   char name[PRODUCT_NAME_MAX + 1];
   char brand[PRODUCT_BRAND_MAX + 1];
   unsigned price;
   unsigned qty;
   struct productNode* nextProduct;
} ProductNodeType;

void print(ProductNodeType *head)
{
   while(head != NULL)
   {
      printf("%s %s\n", head->brand, head->name);
      printf("Price:\t$%u.%u\n", head->price / 100, head->price % 100);
      printf("Qty: %u\n", head->qty);
      head = head->nextProduct;
   }
}

void insertProductNode(char *brand, char *name, unsigned price, unsigned qty, ProductNodeType **head){
   ProductNodeType *node = malloc( sizeof(ProductNodeType) );
   ProductNodeType *iter = *head;
 
   if( node == NULL ){
      fprintf(stderr, "Error allocating memory. addProductNode()");
      exit(EXIT_FAILURE);
   }
 
   /* add data to newly created node */
   strncpy( node->brand, brand, PRODUCT_BRAND_MAX );
   strncpy( node->name, name, PRODUCT_NAME_MAX );
   node->qty = qty;
   node->price = price;
   node->nextProduct = NULL;
 
   if( iter == NULL ){
      *head = node;
   }
   else{
      while( iter != NULL ){
         if( iter->nextProduct == NULL ){
            iter->nextProduct = node;
            break;
         }
         else if ( strcmp( node->name, iter->name ) > 0){
            printf("node->name %s\niter->name %s\n\n", node->name, iter->name);
            node->nextProduct = iter->nextProduct;
            iter->nextProduct = node;
            break;
         }
         iter = iter->nextProduct;
 
      }
 
   }
}

int main()
{
   ProductNodeType *head = NULL;

   insertProductNode("Wonder", "bread", 129, 10, &head);
   insertProductNode("Uncle Ray's", "potato chips", 99, 12, &head);
   insertProductNode("Prince", "spaghetti", 240, 15, &head);
   insertProductNode("Kellog", "cereal", 129, 10, &head);

   print(head);
   
   while (head != NULL)
   {
      ProductNodeType *del = head;
      head = head->nextProduct;
      free(del); 
      del = NULL;
   }  
   return 0;
}

/*
node->name spaghetti
iter->name bread

node->name cereal
iter->name bread

Wonder bread
Price:	$1.29
Qty: 10
Kellog cereal
Price:	$1.29
Qty: 10
Prince spaghetti
Price:	$2.40
Qty: 15
Uncle Ray's potato chips
Price:	$0.99
Qty: 12
*/

C code - 85 lines - codepad

Unless this doesn't fit your expectations somehow?

What do you get?

In fact, if I use your function, they are inserted in the same order as the csv file.

Perhaps you meant to sort by brand instead? In fact, why are you making me guess as much as possible?

I'm not sure what else to provide! I'm guessing here too.
Thanks for your help. I'll keep looking

OK, I'm going to stop thinking so hard.

Revert to what you had when you first posted the thread. Now remove the break statements in your insert function. Report back.

If I remove either of the breaks it seems to just hang (or loop infinitely).
I'm starting to think my logic is off a bit here. I think I've been looking at it for too long.

Thanks iMalc. As I thought, I need to go back and start again.

Fixed it for anyone interested

Code:

void insertProductNode(char *brand, char *name, unsigned price, unsigned qty, ProductNodeType **head){
   ProductNodeType *node = malloc( sizeof(ProductNodeType) );
   ProductNodeType *current = NULL;
   ProductNodeType *previous = NULL;

   if( node == NULL ){
      fprintf(stderr, "Error allocating memory. addProductNode()");
      exit(EXIT_FAILURE);
   }

   strncpy( node->brand, brand, PRODUCT_BRAND_MAX );
   strncpy( node->name, name, PRODUCT_NAME_MAX );
   node->qty = qty;
   node->price = price;
   node->nextProduct = NULL;


   current = *head;
   previous = NULL;

   while( current != NULL && strcmp( current->name, node->name ) < 0 ){
      previous = current;
      current = current->nextProduct;
   }

   node->nextProduct = current;

   if( previous == NULL ){
      *head = node;
   }
   else{
      previous->nextProduct = node;
   }

}