Concatenation Linked List

[deepak643]

Here is my program.. I am unable to concatenate the 2 linked lists using operator overloading. I have got the output of the concatenation once and then again i am not getting it. it is compiling but stucks in run time. Please help me.

#include <iostream>
#include <string>

using namespace std;

class LinkedList
{
    public:
    struct Node
    {
        string value;
        Node *next;
    }*p;

    LinkedList()
    {
        p = NULL;
    }

    /*~LinkedList()
    {
        delete p;
    }*/
    void printAll();
    void addLast(string name);
    void addFirst(string name);
    void removeFirst();
    void removeLast();
    void getFirst();
    void getLast();

   LinkedList operator+(const LinkedList &l);
};


LinkedList LinkedList::operator+(const LinkedList &l)
{
    LinkedList l1 = *this;
    Node *tmp= l1.p;

    while(tmp!=NULL)
    {
        tmp=tmp->next;
    }
    tmp->next = l.p;

    return l1;
}

void LinkedList::getFirst()
{
    if(p!=NULL)
    {
        cout<<"The first node in the list is: "<<p->value<<endl;
    }
}

void LinkedList::getLast()
{
    Node *tmp=p;
    while(tmp!=NULL)
    {
        tmp=tmp->next;
    }

    if(tmp->next==NULL)
    {
        cout<<"The last node in the list is: "<<tmp->value<<endl;
    }
}

void LinkedList::printAll()
{
    if(p==NULL)
    {
        cout<<"There are no nodes in the list"<<endl;
        return;
    }
    else
    {
        Node *tmp = p;
        cout<<endl<< "The nodes in the list are: ";

        while(tmp!=NULL)
        {
            cout << tmp->value<<" ";
            tmp=tmp->next;
        }
    }
}

void LinkedList::addFirst(string name)
{
    if(name.length()>4)
    {
        cout<<" The string having more than 4 characters could not be inserted into the list"<<endl;
        return;
    }
    else
    {
            Node* tmpFirst = new Node;

            tmpFirst->value=name;
            tmpFirst->next=p;

            p=tmpFirst;
    }
}

void LinkedList::addLast(string name)
{
    if(name.length()>4)
    {
        cout<<" The string having more than 4 characters could not be inserted into the list"<<endl;
        return;
    }
    else
    {
        Node *tmpLast = new Node;
        tmpLast->value=name;
        tmpLast->next=NULL;

        if(p==NULL)
            p=tmpLast;
        else
        {
            Node *tmp=p;

            while(tmp->next!=NULL)
            {
                tmp=tmp->next;
            }
            tmp->next=tmpLast;
        }
    }
}

void LinkedList::removeFirst()
{
    if(p==NULL)
    {
        cout<<"The list is empty"<<endl;
        return;
    }
    else
    {
        Node *tmp=p;
        p=p->next;
        tmp->next=NULL;

        delete tmp;
    }
}

void LinkedList::removeLast()
{
    if(p==NULL)
        return;
    else
    {
        Node *tmp=p;
        Node *tmp1=p;

        while(tmp->next!=NULL)
        {
            tmp=tmp->next;
        }
        while(tmp1->next!=tmp)
        {
            tmp1=tmp1->next;
        }
        tmp1->next=NULL;
    }
}

int main()
{
    LinkedList list1;
    LinkedList list2;
    LinkedList list3;

        list1.addFirst("asda");
        list2.addLast("fdgs");
        list1.printAll();
        list2.printAll();
        list1+list2;
        list1.printAll();
}

[helios]

The loop on line 41 causes the iteration node to be null once the loop ends, so the assignment on line 45 dereferences a null pointer. Try to come up with a condition for the loop that will fix this.

[deepak643]

it worked Helios.. In while statement i kept while(tmp->next!=NULL) and it worked :)

[deepak643]

when i add the copy constructor to the same code, its stucking at the run time. I dnt understand why


#include <iostream>
#include <string>

using namespace std;

class LinkedList
{
public:
struct Node
{
string value;
Node *next;
}*p;

LinkedList()
{
p = NULL;
}

/*~LinkedList()
{
delete p;
}*/
void printAll();
void addLast(string name);
void addFirst(string name);
void removeFirst();
void removeLast();
void getFirst();
void getLast();

LinkedList operator+(const LinkedList &l);
LinkedList(const LinkedList &l);
};

LinkedList::LinkedList(const LinkedList &l)
{
Node* tmp = l.p;

while (tmp!=NULL)
{
Node* tmpcopy = new Node;
tmpcopy->value = tmp->value;
tmp = tmp->next;
}
}

LinkedList LinkedList::operator+(const LinkedList &l)
{
LinkedList l1 = *this;
Node *tmp = l1.p;

while(tmp->next!=NULL)
{
tmp=tmp->next;
}
tmp->next = l.p;

return l1;
}

void LinkedList::getFirst()
{
if(p!=NULL)
{
cout<<"The first node in the list is: "<<p->value<<endl;
}
}

void LinkedList::getLast()
{
Node *tmp=p;
while(tmp!=NULL)
{
tmp=tmp->next;
}

if(tmp->next==NULL)
{
cout<<"The last node in the list is: "<<tmp->value<<endl;
}
}

void LinkedList::printAll()
{
if(p==NULL)
{
cout<<"There are no nodes in the list"<<endl;
return;
}
else
{
Node *tmp = p;
cout<<endl<< "The nodes in the list are: ";

while(tmp!=NULL)
{
cout << tmp->value<<" ";
tmp=tmp->next;
}
}
}

void LinkedList::addFirst(string name)
{
if(name.length()>4)
{
cout<<" The string having more than 4 characters could not be inserted into the list"<<endl;
return;
}
else
{
Node* tmpFirst = new Node;

tmpFirst->value=name;
tmpFirst->next=p;

p=tmpFirst;
}
}

void LinkedList::addLast(string name)
{
if(name.length()>4)
{
cout<<" The string having more than 4 characters could not be inserted into the list"<<endl;
return;
}
else
{
Node *tmpLast = new Node;
tmpLast->value=name;
tmpLast->next=NULL;

if(p==NULL)
p=tmpLast;
else
{
Node *tmp=p;

while(tmp->next!=NULL)
{
tmp=tmp->next;
}
tmp->next=tmpLast;
}
}
}

void LinkedList::removeFirst()
{
if(p==NULL)
{
cout<<"The list is empty"<<endl;
return;
}
else
{
Node *tmp=p;
p=p->next;
tmp->next=NULL;

delete tmp;
}
}

void LinkedList::removeLast()
{
if(p==NULL)
return;
else
{
Node *tmp=p;
Node *tmp1=p;

while(tmp->next!=NULL)
{
tmp=tmp->next;
}
while(tmp1->next!=tmp)
{
tmp1=tmp1->next;
}
tmp1->next=NULL;
}
}

int main()
{
LinkedList list1;
LinkedList list2;
LinkedList list3;
LinkedList list4;



list1.addFirst("asda");
list2.addLast("fdgs");
list1.printAll();
list2.printAll();
list4 = list2;
list4.printAll();
list3 = list1+list2;
list3.printAll();

}