Member Avatar for boka123

The program should insert a node that is a sum of next 2 nodes

stdin: 2->7->4->9;

stdout: 2->11->7->13->4->9;

The program returns a segmentation fault,I'm not sure what seems to be the problem.

void insert(Node * list){

   if (list==NULL) {

   return;

    }

for(; (list->next->next)!=NULL ; list=list->next){

 Node* new=(Node*)malloc(sizeof(Node));

  if(new == NULL)

   return;

else {

 new->data= (( list->next->next )->data )+( (list->next)-> data );

  new->next = list->next;

   list->next = new;

list = list->next->next ;

     }
   }
 }
  • 3 Contributors
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  • 3 Days Discussion Span
  • Latest Post Latest Post by Akash_Soni
Member Avatar for L7Sqr

Inserting a node that is the sum of the next two nodes creates an infinite process. Consider:

Original: 1 -> 2 -> 3 -> 4
Iteration 1:
          1 -> 2 -> 3 -> 4
          ^ (add 2 + 3, insert node)
          1 -> 5 -> 2 -> 3 -> 4
               ^ (increment pointer)
Iteration 2:
          1 -> 5 -> 2 -> 3 -> 4
               ^ (add 2 + 3, insert node)
          1 -> 5 -> 5 -> 2 -> 3 -> 4
                    ^ (increment pointer)

You can see that you will never get to the end of the list if you continue to grow it.

As for why you get your issues, you are not checking all the pointers you are dereferencing. Consider:

if (list==NULL) {
   return;
}

for(; (list->next->next)!=NULL ; list=list->next) {
   // ...
}

What happens when list->next is NULL?

Member Avatar for Akash_Soni

Remove the statement 25 and in line 9 in for loop change

list=list->next

with

list=list->next->next
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