Swap nodes in a linked list without swapping data

#include<stdio.h>

// Structure of Node
struct node
{
int data;
struct node *next;
};
typedef struct node node;

//Function to insert data in linked list
void insert(node **ptr,int val)
{
node *nn=(node*)malloc(sizeof(node));
nn->data=val;
nn->next=*ptr;

/*Move start Pointer to head*/
*ptr=nn;
}

//Function to print linked list
void printList(node *ptr)
{
   while(ptr!=NULL)
   {
     printf("%d ",ptr->data);
     ptr=ptr->next;
   }
}

//Function to swap nodes
void swapNode(node **head,int val_1,int val_2)
{
//If both values are same nothing to do
if(val_1==val_2)
return;

   //Search for val_1
   node *ptr_1=*head,*prev_1=NULL;
   while(ptr_1 && ptr_1->data!=val_1)
   {
     prev_1=ptr_1;
     ptr_1=ptr_1->next;
   }
    //Search for val_2
   node *ptr_2=*head,*prev_2=NULL;
   while(ptr_2 && ptr_2->data!=val_2)
   {
     prev_2=ptr_2;
     ptr_2=ptr_2->next;
   }
 
   //Value not found
   if(ptr_2==NULL || ptr_1==NULL)
   return;
 
   if(prev_1!=NULL)
     prev_1->next=ptr_2;
   else
     *head==ptr_2;
   
   if(prev_2!=NULL)
     prev_2->next=ptr_1;
   else
     *head=ptr_1;
   
   // Swap next pointers
   struct node *temp = ptr_1->next;
   ptr_1->next = ptr_2->next;
   ptr_2->next  = temp;
   
}

int main()
{
   node *start=NULL;
     /* The linked list is:
     1->2->3->4->5->6->7 */
   insert(&start,7);
   insert(&start,6);
   insert(&start,5);
   insert(&start,4);
   insert(&start,3);
   insert(&start,2);
   insert(&start,1);
 
   /*Before Swap LinkList*/
   printf("\nLinked List Before Swap of Nodes :");
   printList(start);

   swapNode(&start,3,5);
 
    /*After Swap LinkList*/
   printf("\nLinked List After Swap of Nodes  :");
   printList(start);
   return 0;
}