Help with pointers

[teddarr]

I am trying to write a program that will use pointers and dynamic variables to create a linked list. I need help reading the external file and placing those integers in the list. Then I need help arriving at the sum of those integers.

Here's what I've got so far:

#include <iostream>
#include <iomanip>
#include <fstream>
 
using namespace std;
 
ifstream filein;
 
struct nodetype;    //forward, incomplete declaration
typedef nodetype *nodeptrtype;
 
struct nodetype
{
    int num;
    nodeptrtype ptr;
    nodeptrtype sumptr;
};
//main()***************************************************
void main()
{
 
    filein.open("E:INTFILE.DAT");  //opens external file that contains several (28) random integers
 
    nodeptrtype sumptr;
    nodeptrtype front, auxptr, endptr;
    int numin;
    int sum = 0;
 
 
//this segment creates a linked list by placing each new mode
    //at the end of the list
        front = new nodetype;
        front->num = numin;
        front->ptr = NULL;
        endptr = front;
 
    while(filein)
        filein>>auxptr;
 
    do
    {
//        cout<<"Enter an integer.";  used for keyboard input
//        cin>>numin;
 
        if(cin);
        {
            auxptr = new nodetype;
            auxptr->num = numin;
            auxptr->ptr = NULL;
            endptr->ptr = auxptr;
            endptr = auxptr;
        }
    }while(cin);
 
 
 
//This segment traverses the linked list and displays the integers on one line
    //trying to get a sum of the integers but it wont work
    cout<<endl<<endl<<"Values in the first list: "<<endl;
    auxptr = front;
    while (auxptr != NULL)
    {
        cout<<auxptr->num<<" ";
        auxptr = auxptr->ptr;
        sum = sumptr + auxptr;
    }
    cout<<endl<<"The sum of the integers in the linked list is: "<<sum<<endl;
    cout<<endl<<endl;
 
}

Any help will be appreciated.

[teddarr]

Please, Anyone have any ideas?

[horace1]

Please, Anyone have any ideas?

fixed a few things so it now compiles and executes

#include <iostream>
#include <iomanip>
#include <fstream>
 
using namespace std;
 
ifstream filein;
 
struct nodetype;    //forward, incomplete declaration
typedef nodetype *nodeptrtype;
 
struct nodetype
{
    int num;
    nodeptrtype ptr;
    nodeptrtype sumptr;
};
//main()********************************************  *******
int main()
{
 
    filein.open("E:INTFILE.DAT");  //opens external file that contains several (28) random integers
 
    nodeptrtype sumptr;
    nodeptrtype front, auxptr, endptr;
    int numin;
    int sum = 0;
 
 
//this segment creates a linked list by placing each new mode
    //at the end of the list
        front = new nodetype;
        front->num = numin;
        front->ptr = NULL;
        endptr = front;
 
//    while(filein)               // ** removed ??
    //    filein>>auxptr;         // ** removed
 
    do
    {
//        cout<<"Enter an integer.";  used for keyboard input
//        cin>>numin;
 
        if(cin>>numin);   // ** read next number
        {
            auxptr = new nodetype;
            auxptr->num = numin;
            auxptr->ptr = NULL;
            endptr->ptr = auxptr;
            endptr = auxptr;
        }
    }while(cin.good());      // ** test if cin is OK
 
 
 
//This segment traverses the linked list and displays the integers on one line
    //trying to get a sum of the integers but it wont work
    cout<<endl<<endl<<"Values in the first list: "<<endl;
    auxptr = front;
    while (auxptr != NULL)
    {
        cout<<auxptr->num<<" ";
        auxptr = auxptr->ptr;
        sum = sum + auxptr->num;    // ** fixed ??
    }
    cout<<endl<<"The sum of the integers in the linked list is: "<<sum<<endl;
    cout<<endl<<endl;
 
}
 

it reads from the keyboard at the moment - you can change to read from your data file

when I ran the program entering 1 2 3 4 5 6 ctrl/z it gave
1
2
3
4
5
6
^Z
Values in the first list:
14 1 2 3 4 5 6 6

then crashed with a segmentation error - clearly still got some problems but can probably solve them now

[DeMan]

I think there are 2 problems with the code....
Firstly front is declared but never set to anything (hence the first strange output)
Secondly, [ctrl z] is a character and is added to the list, so we read too many elements.

I have messed around with(that is modified) it and have somethiong I think works....

#include <iostream>
#include <iomanip>
#include <fstream>
 
using namespace std;
 
ifstream filein;
 
struct nodetype;    //forward, incomplete declaration
typedef nodetype *nodeptrtype;
 
struct nodetype
{
    int num;
    nodeptrtype ptr;
    nodeptrtype sumptr;
};
//main()********************************************    *******
int main()
{
 
    filein.open("E:INTFILE.DAT");  //opens external file that contains several (28) random integers
 
    nodeptrtype sumptr;
    nodeptrtype front=NULL; 
    nodeptrtype auxptr, endptr;
    int numin;
    int sum = 0;
 
 
    do
    {
 
        if(cin>>numin);   // ** read next number
        {
            if(front==NULL)
            {
              front = new nodetype;
              front->num = numin;
              front->ptr = NULL;
              endptr = front;
           } 
           else
           {   
            auxptr = new nodetype;
            auxptr->num = numin;
            auxptr->ptr = NULL;
            endptr->ptr = auxptr;
            endptr = auxptr;
          }
        }
    }while(cin.good());      // ** test if cin is OK
 
 
 
//This segment traverses the linked list and displays the integers on one line
    //trying to get a sum of the integers 
    cout<<endl<<endl<<"Values in the first list: "<<endl;
    auxptr = front;
    while (auxptr->ptr != NULL)
    {
          cout<<"fred";
        cout<<auxptr->num<<" ";
        auxptr = auxptr->ptr;
        sum = sum + auxptr->num;    // ** fixed ??
    }
    cout<<endl<<"The sum of the integers in the linked list is: "<<sum<<endl;
    cout<<endl<<endl;
    getchar();
}
 
 

[teddarr]

Thanks, I'll work with that.