Link list

utkarshrawat · 04-12-2012, 11:54 PM

Below is a simple example of single link list I have one question , what does this statement means
q=q->link;

Code:

 struct node
{
	int info;
	struct node *link;
}*start;


int create(int data)
{
	struct node *q,*tmp;
	tmp=malloc(sizeof(struct node));
	tmp->info=data;
	tmp->link=NULL;
	
	if(start==NULL) 
		start=tmp;  
	else
	{	
		
		q=start;    
		while(q->link!=NULL)
		{
			q=q->link;
		}
		
			q->link=tmp;		
	}
	return(1);
}

Thanks in advance

pan64 · 04-13-2012, 02:03 AM

The struct q has two members, q.info is an int and q.link is a pointer to another struct (type of node)
q->link is the struct itself pointed by the member link.
q = q->link means give q a new value, the node pointed by the member link.

this is a pretty simple linked list, all elements has a link to the next one.

the create function will look for the last element in the list and add a new one to it.

utkarshrawat · 04-13-2012, 02:23 AM

Thanks for the reply .I have one more doubt how this statement q=q->link is differ from
q->link=tmp
So let say I have 3 numbers
1
2
3
first for 1 it will go to

Code:

 if(start==NULL) 
		start=tmp;// This means it will store the value of tmp to start i.e. 1

then for 2 it will go to else part

Code:

 else	
	     {	
		q=start;  //Here it will store value start to q   
		while(q->link!=NULL) //Since q is not not null it not go into q=q->link 
		    {
			q=q->link;
		    }
		       q->link=tmp; //Here I came to know we are storing value 2 ,what this statement means		
	     }

pan64 · 04-13-2012, 02:52 AM

Code:

int create(int data)
{
	struct node *q,*tmp;                    # this line defines the variables q and tmp as pointers to struct node
	tmp=malloc(sizeof(struct node));        # allocate memory for a struct (create new item)
	tmp->info=data;                         # fill up the struct, info = data
	tmp->link=NULL;                         #                     link = null (no next item)
	
	if(start==NULL)                         # start = null, list is empty
		start=tmp;                      #       tmp is the first, so store this as start of the list
	else
	{	
		
		q=start;                        # start was not null, try to find the last element of the list
		while(q->link!=NULL)            # while we have a next element
		{
			q=q->link;              # take it
		}
		
			q->link=tmp;		# we found the last (link is null), so we can store the new element (tmp) now
	}
	return(1);
}