link list

[vishal Tripathy]

I am trying to wtite a programme for link list using class.I don't know the the error in deleting in the fuction del1 in the class linklist . Please check the error.

  #include<iostream>
#include<string>
using namespace std;
class linklist
{
    public:
    linklist *ptr;
    string n;
    int j,a;
    void input(string* b)
    {
        n=*b;
    };
    string taken()
    {
        return n;
    };
    void input1(int* b)
    {
        a=*b;
    };
    int taken1()
    {
        return a;
    };
    void display()
    {
        cout<<n<<endl;
        if(ptr!=NULL)
        ptr->display();
    };
    void search(string d)
    {
        linklist *ptr1;
        int i=1;
        j=0;
        if(d==n)
        {
            j++;
            cout<<i<<"\n";
        }
        if(ptr!=NULL)
            {
                i++;
            if(d==ptr->taken())
            {
                j++;
                cout<<i<<"\n";
            }
            ptr1=new linklist;
                ptr1=ptr->ptr;
            }
            cc:
            if(ptr1!=NULL)
            {
                i++;
            if(d==ptr1->taken())
            {
                j++;
                cout<<i<<"\n";
            }
                ptr1=ptr1->ptr;
                goto cc;
            }
            else
            {
                if(j==0)
                cout<<"not found\n";
            }
    };
    void position(int m)
    {
        linklist *ptr1;
        if(m==1)
        cout<<n<<"\n";
        else
        {
            if(m==2)
            {
                if(ptr!=NULL)
                cout<<ptr->taken()<<"\n";
                else
                cout<<"there is no number\n";
            }
            else if(m==3)
            {
                if(ptr!=NULL)
            {ptr1=new linklist;
            ptr1=ptr->ptr;
            if(ptr1!=NULL)
            cout<<ptr1->taken();
            else
                cout<<"there is no number\n";}
            else
                cout<<"there is no number\n";
            }
            else
            {
                if(ptr!=NULL)
                {ptr1=new linklist;
                    ptr1=ptr->ptr;
                for(int k=2;k<m-1;k++)
                    {
                        if(ptr1!=NULL)
                        ptr1=ptr1->ptr;
                    }
                    if(ptr1!=NULL)
                cout<<ptr1->taken();
                else
                cout<<"there is no number\n";
                }
                else
                cout<<"there is no number\n";
            }
        }
    };
    int del(string b)
    {
        if(n==b)
            return 1;
        else return 0;
};
int del1(string b)
{
        linklist *ptr1,*ptr2,*ptr4,*ptr3,*ptr5;
        int i=1;
        ptr2=new linklist;
        ptr2=NULL;
        if(ptr!=NULL)
        {if(b==ptr->taken())
            {ptr2->input1(&i);
            ptr2->ptr=NULL;}
            ptr1=new linklist;
            ptr1=ptr->ptr;
            if(ptr1!=NULL)
            {
                i++;
            if(b==ptr1->taken())
            {
                ptr3=new linklist;
                ptr3->input1(&i);
                ptr2->ptr=ptr3;
                ptr3->ptr=NULL;
            }
                ptr1=ptr1->ptr;
            }
            cc:
            if(ptr1!=NULL)
            {
                i++;
            if(b==ptr1->taken())
            {
                ptr4=new linklist;
                ptr4->input1(&i);
                ptr3->ptr=ptr4;
                ptr3=ptr4;
            }
                ptr1=ptr1->ptr;
                goto cc;
            }
            }
        if(ptr2==NULL)
        return 1;
        else
        {
        ee:
        if(ptr2!=NULL)
        {
            int k;
            k=ptr2->taken1();
        if(k==1)
        ptr=ptr->ptr;
        else if(k==2)
        {
        string z;
            ptr1=new linklist;
                ptr1=ptr->ptr;
            ptr5=new linklist;
            ptr5=ptr1->ptr;
            ptr->ptr=ptr5;
        }
        else if(k>2)
        {
        string z;
            ptr1=new linklist;
                ptr1=ptr->ptr;
            for(int l=2;l<k;l++)
                ptr1=ptr1->ptr;
            ptr5=new linklist;
            ptr5=ptr1->ptr;
            ptr->ptr=ptr5;
        }
        ptr2=ptr2->ptr;
        goto ee;
        }
        return 0;
        }
    };
};
int main()
{
    cout<<"first enter strings\n";
    cout<<"enter \"end\" to stop entering strings\n";
    linklist *f,*t,*s;
    string m;
    cin>>m;
    f=new linklist;
    f->input(&m);
    cin>>m;
    if(m=="end")
    {
        f->ptr=NULL;
        goto aa;
    }
    t=new linklist;
    t->input(&m);
    f->ptr=t;
    bb:
    cin>>m;
    if(m=="end")
    {
        t->ptr=NULL;
        goto aa;
    }
    else
    {
        s=new linklist;
        s->input(&m);
        t->ptr=s;
        t=s;
        goto bb;
    }
    aa:
    cout<<"1-display\n2-search\n3-more input\n4-exit\n5-position\n6-delete\n";
    int n;
    cin>>n;
    switch(n)
    {
        case 1:
        f->display();
        break;
        case 2:
        cin>>m;
        f->search(m);
        break;
        case 3:
        goto bb;
        break;
        case 4:
        goto dd;
        break;
        case 5:
        int o;
        cin>>o;
        f->position(o);
        break;
        case 6:
        o=0;
        cin>>m;
        hh:
        if(f->del(m)==1)
        {
            o++;
            f=f->ptr;
            if(f!=NULL)
            goto hh;
        }
        else
        if(f->del1(m)==1&&o==0)
        cout<<"there is no such string\n";
        break;
        default:
        cout<<"error";
    }
    goto aa;
    dd:
    delete f,s,t;
    return 0;
}

[1v5E3TCk]

No one can help you until you give the error message, anyway it is named Linked List not linklist

[o3hC5Di1]

Hi there,

if(ptr!=NULL)
{if(b==ptr->taken())

You have declared : linklist *ptr1,*ptr2,*ptr4,*ptr3,*ptr5;, but not ptr.
I'm suspecting you mean:

if(ptr1!=NULL)
{if(b==ptr1->taken())

As senhor mentioned, it is best to state your problem clearly and specifically, including any error messages you get from the compiler, linker or program crash. That helps us to help you better.

Please do let us know if you need any further help.

All the best,
NwN

[vishal Tripathy]

Ther is error report in any other function except del1. It is showing "segmentation fault (core dumped)"

[vishal Tripathy]

Hi, NwN
I have declared *ptr in the class at the beginning.

[o3hC5Di1]

Which platform are you on (windows/linux/...)?
Can you use a debugger (such as gdb)?

Otherwise, you could add std::cout statements to your code to track in the console where your program crashes exactly.

All the best,
NwN

[vishal Tripathy]

I am using Linux.
I am wrting in code blocks.
How can i track? I don't know please help.

[o3hC5Di1]

Please see this link for information specific to code::blocks:
http://wiki.codeblocks.org/index.php?title=Debugging_with_Code::Blocks

With GDB, note that your program needs to be compiled with the "-g" flag, you could do:

#gdb (your program name)
gdb> run
[segfault]
gdb> bt

"bt" will show you a backtrace of where the program crashed. For more information about using GDB to track a segfault, please see: http://www.cplusplus.com/articles/iwTbqMoL/

To use debug output statements, do something like this, but in the whole program:

int main()
{
    cout<<"first enter strings\n";
    cout<<"enter \"end\" to stop entering strings\n";

    std::cout << "--Creating linked list pointers\n";
    linklist *f,*t,*s;
    string m;
    cin>>m;

    std::cout << "--initializing f\n";
    f=new linklist;
    f->input(&m);
    cin>>m;
    if(m=="end")
    {
        std::cout << "--m==end, setting f->ptr=NULL\n";
        f->ptr=NULL;
        goto aa;
    }

//... 

Also, note that the use of "goto" is discouraged. Mostly for purposes like this, it gets really tough to debug a program that just jumps from one place to another with no seeming logic behind it.

All the best,
NwN