Pointer error in Linked list?

Question

I want to create a linked list with integeres and between each two nodes I want to create another node that is the average between the one before and the one after.

In my add function I don't understand why my p pointer is at the last element in the linked list and not at the first. (this is why I think it crashes).

Thank you.

#include<iostream>
using namespace std;

struct Nod{
    int info;
    Nod* urm;
};

void create(const int &a, Nod *&p, Nod *&u)
{
    if (p == NULL)
    {
        p = new Nod;
        p->info = a;
        u = p;
    }
    else
    {
        Nod *q;
        q = new Nod;
        q->info = a;
        u->urm = q;
        u = q;
    }
    u->urm = NULL;
}

void print(Nod *p)
{
    while (p->urm)
    {
        cout << p->info<<" -> ";
        p = p->urm;
    }
    cout << p->info;
}

void add(Nod *p)
{
    while (p)
    {
        Nod *q;
        q = new Nod;
        q->info = (p->info + p->urm->info) / 2;
        q->urm = p->urm;
        p->urm = q;
        p = p->urm->urm;
    }
}

int main()
{
    Nod *p, *u;
    p = u = NULL;

    char *numar;
    numar = new char[100];
    cout << "Enter a number: "; cin >> numar;
    for (int i = 0; (unsigned)i <= strlen(numar) - 1; i++)
        create(numar[i] - '0', p, u);
    add(p);
    print(p);

    system("Pause");
    return 0;
}

Crash Unhandled exception at 0x013C5A78 in L3_P2.exe: 0xC0000005: Access violation reading location 0x00000000. — Stefan
– Stefan, Commented Nov 25, 2014 at 5:34

Pranit Kothari · Accepted Answer · 2014-11-25 05:37:00Z

1

You need to add,

if(p->urm!=0)// this line
        q->info = (p->info + p->urm->info) / 2;

Because p->urm could be NULL.

I tried in Visual Studio after adding suggested line, and it is working fine. Though I do not understand what will you get by adding two addresses.

answered Nov 25, 2014 at 5:37

Pranit Kothari

9,92511 gold badges65 silver badges145 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Ashwani Over a year ago

Also since he are calculating average data type of info should be float

Pranit Kothari Over a year ago

@AshwaniDausodia May be.. but what will he get by adding and then by taking avg..

Collectives™ on Stack Overflow

Pointer error in Linked list?

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related