Thread: A little help with Linked List functions

I need to create a linked list of customer data. One functions needs to insert a new customer data at the location indicated by the parameter "index". If index is 0 then it should be inserted as the first data in the linked list. I think I coded that function right, here it is:

Code:

int insertAtIndex(char * lastname, char * firstname, int id, float balance, int index)
{
    int counter = 0;
    
    struct Contact * newContact, *temp;
    newContact = (struct Contact *) malloc(sizeof(struct Contact));
    
    strcpy(newContact->last_name,lastname);
    strcpy(newContact->first_name,firstname);
    newContact->id = id;
    newContact->balance = balance;
    
    if(head == NULL) 
    { 
      head=newContact; 
      newContact->next = NULL; 
    }
    
    else
    {
      temp = head;
        
      while(counter != index)
      {
       temp=temp->next;
      }          
      newContact->next=NULL; 
      temp->next=newContact;

    }
    return 0;
}

The second function just returns the number of entries in the linked list. Here is that function:

Code:

int size()
{
 struct Contact *conductor;
 conductor = head;
 int total = 0;
 
 while(conductor !=NULL) 
 {
    total++;
    conductor =  conductor->next;
 }
 
 return total;   
}

The third function prints all entries in the linked list it looks like this:

Code:

void displayLinkedList( )
{
  struct Contact *conductor;
  
  conductor = head;
 
     while ( conductor != NULL ) 
     {
       printf("%s\n", conductor->last_name);
       printf("%s\n", conductor->first_name);
       printf("%d\n", conductor->id);
       printf("%f\n", conductor->balance);
       printf("\n");
       conductor = conductor->next;
     }

    
}

Now in my main function I have a switch case to act as a menu. I'm not sure if its my function causing the problems, or a logic error in my do-while switch loop. When I run my program I can always input my first choice fine. But when I try to input my second choice it just automatically goes to the default case in the switch. Here is that-

Code:

do
       {
 
         printf("What action would you like to perform?\n");
 
         choice = getchar();
         getchar(); //to flush '\n'
         choice = toupper(choice);
       
         switch (choice)
         {
              case 'A':
                   printf("Please enter a customer to add: \n");
                   printf("Please enter the last name: \n");
                   
                   i = 0;
                   do
                   {
                       inputChar = getchar(); 
                       if (inputChar != '\n' && inputChar != '\r')
                       {
                          *(last_name + i) = inputChar;
                       }
 
                       i++;
                    } while (i < 50 && inputChar != '\n' && inputChar != '\r');
                    *(last_name + i) = '\0';
                    
                    printf("Please enter the first name: \n");
                    
                    i = 0;
                    do
                    {
                        inputChar = getchar();
                        if (inputChar != '\n' && inputChar != '\r')
                        {
                           *(first_name + i) = inputChar;
                        }
                        
                        i++;
                    } while (i<50 && inputChar != '\n' && inputChar != '\r');
                   *(first_name + i) = '\0'; 
                   
                   printf("Please enter the id(number): \n");
                   scanf("%d", &id);
                   
                   printf("Please enter the balance: \n");
                   scanf("%f", &balance);
                   
                   printf("Please enter the index to insert: \n");
                   scanf("%d",&index);
                   
                   bool_index = insertAtIndex(last_name, first_name, id, balance, index);
                   if(bool_index < 0)
                     printf("The Customer could not be added\n");
                    else
                        printf("The Customer is added at %d\n", index); 
                   
                   break;
                  
              case 'D':
                   printf("The size of the linked list is %d\n", size());
                   break;
               
              case 'P':
                   if(size() == 0)
                         printf("The list is empty\n");
                   else
                         displayLinkedList( );
                   break;
              
              /*case 'R':
                   printf("Please enter an id(number) to remove: \n");
                   scanf("%d", &id);
                   bool_remove = removeCustomer(id);
                   
                   if(bool_remove < 0)
                         printf("Customer with the id was not found");
                   else
                         printf("Customer was removed");  
                        
                   break;
                   
               case 'S': */                                   
                   
              default:
                   printf("Unknown action\n");
                   break;
         }
       } while (choice != 'Q');

Any help would be appreciated.

So if you have three entries in the list and you try to insert at index 5.....

I think I understand what you're implying, however after working on the function again today for hours I'm still having the same problem. I ended up with three different functions and none of them working properly Heres is the cleanest one:-

Code:

int insertAtIndex(char * lastname, char * firstname, int id, float balance, int index)
{
    int i;
    
    struct Contact * newContact, *conductor;
    conductor = head;
    
    newContact = (struct Contact *) malloc(sizeof(struct Contact));
    
    strcpy(newContact->last_name,lastname);
    strcpy(newContact->first_name,firstname);
    newContact->id = id;
    newContact->balance = balance;
    
    newContact->next = NULL;
    
    if(conductor == NULL) 
    { 

      head=newContact; 
      newContact->next = NULL; 
    }
    
    else
    {
    
        
      for(i = 0; i< index; i++)
      {
       conductor=conductor->next;
       
      }           
      conductor->next=newContact;

    }
        
    return index;
}