Segmentation fault in mersort

#1

I tried implementing the merge sort code for linked list. It is giving segmentation fault. I checked the midpoint function it is working properly and the insertattail is also working properly i guess the fault is in mergesorted function can you please help me correct that function?

#2

Hey @prerna_gupta31
There are 2 corrections

node * mergesorted(node *& a, node *& b)
{
    if(a==NULL)
    {
        return b;
    }
    else if(b==NULL)
    {
        return a;
    }
    node * result ;
    if(a->data<=b->data) //coorecte this
    {
        result = a;
        result->next = mergesorted(a->next,b);
    }
    else
    {
        result = b;
        result->next = mergesorted(a,b->next);
    }
    return result;
}
node * mergesort(node * &head)
{
    if(head==NULL || head->next==NULL)
    {
        return head;
    }
    node * m = midpoint(head);
    node * a = head;
    node * b = m->next;
    m->next=NULL; //added this
    a = mergesort(a);
    b = mergesort(b);
    node * c = mergesorted(a,b);
    return c;
}
#3

If this resolves your query then please mark it as resolved :slight_smile:

#4

thanks it solved the problem but what is the significance of this m->next=NULL; ?

#5

When we apply mergesort in arrays we work on smaller arrays right

If we don’t apply m->next=NULL then first list will always be equal to bigger list hence giving unwanted results