Question

Ive gone through some of the previous posts on Stack Overflow before posting this.
Everytime I try to run this on ideone.com (which uses the SPOJ engine) I get a SIGSEGV runtime error and I am stumped.
Can anyone please help me out? Ive commented the line where I think I might have gone wrong..

//MY CODE TO INSERT INTO A LINKED LIST
#include<iostream>
#include<malloc.h>

using namespace std;

struct Node
{
int data;
struct Node *link;
};
struct Node *node =NULL; //suspected error..not sure

void insert(int item)
{
if(node==NULL)
{
       node->data=item;
       node->link=NULL;
}
else 
{
    struct Node *temp;
    temp=node->link;
    node->data=item;
    node->link=temp;
}
} 

void display()
{
if(node==NULL)
    cout<<"Linked list is empty!";
while(node!=NULL)
{
    cout<<node->data<<" ";
    node=node->link;
}
}         
int main()
{
int n;
    cin>>n;
    display();
    insert(n);

      display();
return 0;
}

Answer 1

You are not allocating memory to the Node. You need to do this in your insert function:

node = new Node();

And only after that, you should start filling out data and link in your node. Do this in both if and else cases.

The corrected code will be something like the following (I haven’t run it through a compiler, so check for compiler errors):

void insert(int item)
{
if(node==NULL)
{
       node = new Node();
       node->data=item;
       node->link=NULL;
}
else 
{
    struct Node *temp = new Node();
    temp=node->link;
    node->data=item;
    node->link=temp;
}
} 

You also need to delete all the allocated nodes later on after you have finished working with the list, otherwise, it will be a memory leak.