Question

Need some help creating a bubble sort for my linked list in C. Here are the structs used in my code:

struct simulation
{
   void *list;
   int et; /* in seconds */
};
struct plane
{
   double x, y, altitude;
   char callsign[15];
   struct simulation *sim;

};
Here is the struct used in my linked list:
struct Node
{
   void *data;
   struct Node *next;
};

Here is my insert function:
//ComparisonFunction and FILE not critical to the function at the moment.
int insert (void *p2head, void *data, ComparisonFunction goesInFrontOf, FILE *diagnostics)
{
   struct Node *newNode = (struct Node*) malloc(sizeof(struct Node));
   struct Node **head_ref = (struct Node** )p2head;

   if (newNode == NULL)
   {
       printf("ERROR!\n");      
       return 0;
   }
  
   newNode->data = data;
   if(newNode != NULL && goesInFrontOf(newNode->data, data))
   {  
       newNode->next = *head_ref;
       (*head_ref) = newNode;

   }
   return 1;
}
Insert is called like so in a function:
void add_plane_to_sim(struct plane *fake, struct simulation *sim)
{
   struct plane *real;
   if( real = allocate_plane(sim->diagnostics)) //allocate_plane just allocates a struct using calloc and statically counts   
//successful allocations. allocate_plane returns a struct.
   {
        /* copy the data and toss on the list */
        *real = *fake;
        insert(&sim->list, real);
   }
   /* no else - allocate plane already complained */
}

Now I need to create a sorting function, which can use the bubble sort algorithm. Here is the declaration:
/* sort moves data, not nodes, so head won't change */
void sort(void *head, ComparisonFunction goesInFrontOf)
{
    ....
}
Sort is called like so: sort(sim->list, westmost);

I'm not too sure how to go about doing this. I don't know how to move data within the nodes so I can sort them by data and not manipulate the nodes. Providing all of my code would be too much as its in 4 different files. The only issue I have is with the sort function. A function pointer is used as the second parameter to sort the data based off of position data. Ive attached the code the ComparisonFunction will call below. The sort function cannot call the plane or sim structure. It can only call the node struct like shown in my insert function. I hope this is enough code to work with. Any help would be great thank you!

int westmost(void *west, void *east) //call for comparison function
{
   struct plane *w, *e;
   w = west;
   e = east;
   return(w->x <= e->x);
}

I need to complete the sort function, but im not sure how. Sort needs to sort the linked list by data. I am passing sim->list to sort, the sorting function cant know the type of structure it is which is why it takes a void pointer. The only structure sort can see is struct Node. sort needs to use the void pointer to sort data within the linked list. A comparison will be made with the second parameter that will determine if the position is out of view (data in another file, not needed since westmost does the calculation). I'm just not sure how to do a bubble sort of data on a void pointer.

Answer 1

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

struct node
{
int data;
struct node *next;
};
typedef struct node nd;
nd *start=0;
int count=0;
void insert_at_end(int item)
{
nd *temp,*head;
head=(int*)malloc(sizeof(nd));
head->data=item;
head->next=0;
if(start==0)
start=head;
else
{
temp=start;
while(temp->next!=0)
temp=temp->next;
temp->next=head;
}
count++;
}
void bubble_sort()
{
nd *temp2;
int i,j,temp_int;
for(i=0;i<count-1;i++)
{
temp2=start;
for(j=0;j<count-i-1;j++)
{
if(temp2->data>temp2->next->data)
{
temp_int=temp2->data;
temp2->data=temp2->next->data;
temp2->next->data=temp_int;
}
temp2=temp2->next;
}
}

}
void display()
{
nd *temp=start;
bubble_sort();
while(temp!=0)
{
printf("%d=>",temp->data);
temp=temp->next;
}
printf("NULL");
}
void main()
{
int choice,item;
while(1)
{
printf("\n1.Enter at the end of linked list");
printf("\n2.Display sorted linked list");
printf("\nEnter your choice:");
scanf("%d",&choice);
switch(choice)
{
case 1:
printf("Enter a number to insert:");
scanf("%d",&item);
insert_at_end(item);
break;
case 2:
display();

}
}
}