need help with Tracking user login

Here is the topic

[FONT=helvetica, arial, verdana, 'ms sans serif', sans-serif]Each user has a unique five-digit ID number.Whenever a user logs on, the users's ID,lab number,and the computer station number are transmitted to your system.For example,if the user 49193 logs onto station 2 in lab 3, then your sytem recieves(49193,2,3) as input data.Similarly,when a  user logs off a station,then your system receives the lab number and computer station number. write a computer program that could be used to track,by lab which user is logged onto which computer. Create a menu that allows the administrator to simulate the transmission of information by manually typing in the login or logoff data.Whenever someone logs in or out, the display should be update.Also write a search function so that the administrator can type in a use ID and the system will output the lab and station number that user is logged into, or NONE if the user is not logging to any computer.[/FONT]

Code:

---

#include <iostream>#include <cstdlib>


using namespace std;


int **dynArray(int row, int cols)
{
    int **myPtr;
    myPtr = new int *[row];
    for(int i = 0; i < row; i++)
    myPtr[i] = new int[cols];
    for(int i = 0; i<row ; i++)
    if(myPtr[i] == 0)
    cout<<"empty";
   
    return myPtr; 
}
void getinput(int &ID,int &Station,int &labnumb)
{
    cout<<" Enter your ID number: "<<endl;
    cin>>ID;
      cout<<" Enter your station number: "<<endl;
    cin>>Station;
      cout<<" Enter your lab number: "<<endl;
    cin>>labnumb;
    return; 
}
void getoutput(int &ID,int &Station,int &labnumb)
{
    cout<< "You have been logged out."<<endl;
    return;
}
void login(int **dynArray,int &ID,int &Station,int &labnumb)
{
    dynArray[labnumb][Station] = ID;
    return;
   
}
void search(int **dynArry)
{
   
}   


void Menu(int **dynArray,int &ID,int &Station,int &labnumb)
{
    int choice;
    cin>>choice;
    if(choice == 1)
        login(**dynArray,ID,Station,labnumb);
    if(choice == 2)
        search() //This is input later on
}


int main()
{
    int **lab;
    lab = new int*[4];
    for(int i = 0; i <4 ; i++)
    {
            *(lab + i) = new int;
    }
   
   
   


       
    lab = dynArray(4,7);
 
      system("PAUSE");
      return 0;
}
;

---

I don't know how to declare and write the search function. Also, I need help with what do I need to add to complete the program.Because I kind of mess up everything up@@ If anyone can suggest me to do more thing or less Thanks

Unless int** is specifically part of your assignment, I would suggest you replace it with
std::vector< std::vector<int> >

and just pass it (by reference) from one function to another.

I have consider about using vector but i'm not comfortable to use the vector, so that's why I do it this way and here is second version i get so far, the big problem here I don't know do I need to add the adminstration for another function or what because the topic say search function only for admin use. Therefore, am I thinking right or wrong?????

Code:

---

#include <iostream>#include <cstdlib>


using namespace std;


int **dynArray(int row, int cols)
{
    int **myPtr;
    int lab[4];
    myPtr = new int *[row];
    for(int i = 0; i < row; i++)
    myPtr[i] = new int[lab[i]];
    for(int i = 0; i<row ; i++)
    if(myPtr[i] == 0)
    cout<<"empty";
   
    return myPtr; 
}
void getinput(int ID,int &Station,int &labnumb)
{
    cout<<" Enter your ID number: "<<endl;
    cin>>ID;
      cout<<" Enter your station number: "<<endl;
    cin>>Station;
      cout<<" Enter your lab number: "<<endl;
    cin>>labnumb;
    return; 
}
void logout(int ID,int &Station,int &labnumb)
{
   
    cout<< "You have been logged out."<<endl;
    return;
}
void login(int **dynArray,int ID,int &Station,int &labnumb)
{
    dynArray[labnumb][Station] = ID;
    return;
   
}
bool search(int **dynArry,int ID,int &row,int &cols,int lab[])
{
    cout<<"Enter user ID to check: "<<endl;
    cin>>ID;
    bool found = false;
    for(int i = 0; i < row;i++)
    for(int j = 0; j < lab[i];j++)
    if(ID == dynArry[i][j])
    {
      found = true;
      row = i;
      cols = j;
     
      }
    return found;
}   


void Menu(int **dynArray,int ID,int &Station,int &labnumb,int lab[])
{
    int choice;
    cout<<"Enter 1 for login, 2 for search,3 for exit. "<<endl;
    cin>>choice;
    if(choice == 1)
        login(dynArray,ID,Station,labnumb);
    if(choice == 2)
        search(dynArray,ID,Station,labnumb,lab);
    if(choice == 3)
        exit(0);
}


int main()
{
    int lab[4];
    lab[0] = 5;
    lab[1] = 6;
    lab[2] = 4;
    lab[3] = 3;
    int **labmain;
    labmain = new int*[4];
    for(int i = 0; i <4 ; i++)
    {
            *(labmain + i) = new int;
    }
   
   
   


       
    labmain = dynArray(4,7);
    int ID,Station,labnumb;
    Menu(dynArray,ID,Station,labnumb,lab);
      system("PAUSE");
      return 0;
}

---

So rather than "get comforable with vectors" by actually confronting the issue and doing some learning, you prefer endless frustration over continually screwing up on mis-managing do it yourself memory allocation.

If you're not going to use all the tools in the C++ box, why bother with C++ at all?

> 13 myPtr[i] = new int[lab[i]];
What is lab[i] here?
It isn't the carefully initialised array in main.

> lines 82 to 86
A complete waste and a memory leak, since line 93 just trashes the pointer with a newly allocated block of memory.

> Menu(dynArray,ID,Station,labnumb,lab);
What - dynArray is a FUNCTION, not an array.

Does this even compile? If not, you should post your error messages as well.

> 13 myPtr[i] = new int[lab[i]];
What is lab[i] here?
The lab[i] is the column because the they have 4 row but it has different cols
From the 82-86 is the labmain pointer point to other 4 small pointer. And each small pointers have one row array but different column.Also, i didn't complete it yet this is the so far i got.
Moreover, the Menu(dynArray,ID,Station,labnumb,lab); is call function isn't it?
Because I always confuse on the call function and I don't know how to make it right.
=>It shows one error from the Menu call function in the int main.

Vectors will make your life so much easier trust me I was anti vector a while back. Now they simplify code so much it makes your life a lot easier same thing with using char*'s and strings, once you get it strings are much nicer. Learn vectors you won't regret it. vector - C++ Reference

With vectors, all you need to do is push_back when a user logs in; then delete when he logs out. To do a search use a for loop with always less than your vector.size(). It makes life simple. If you don't use vectors you better know how many computers are in the lab before you ever begin and when that number changes you need to recompile or reload from an ini file. Vectors will handle all your problems with memory and make the program more flexible.

I'm not sure my teacher let me using the vector because he said if you use vector you won't learn anything.?????

Quote:

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Originally Posted by erictu

I'm not sure my teacher let me using the vector because he said if you use vector you won't learn anything.?

---

If your aim is to implement a dynamic array container like std::vector, then just using std::vector won't teach you anything concerning implementation, though it will teach you something about a possible interface for a dynamic array container.

In this case, your aim is to implement something else. A dynamic array is just implementation detail, so using std::vector makes sense. If your teacher also wants you to learn how to implement as a dynamic array as part of the assignment, then the appropriate thing to do is to first design and implement a dynamic array container, and then use that container to implement what you want to implement.

that's the way I'm doing now but I get stuckT_T

Use a struct then with your information ID computer# etc. use your struct as the array type then

but the struct is the next chapter, it's not this chapter:(

Quote:

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Originally Posted by erictu

but the struct is the next chapter, it's not this chapter

---

Right. Are you sure you are not over-complicating things? You just need one integer variable, not a dynamic array of them, to store "a unique five-digit ID number".

Use oversized arrays with full values of -1 to represent open spaces. Write a function that looks for a -1 in one array(doesn't matter which) then places your data in all 3 arrays you have to store data. You can loop and look for values != -1 to see who is logged in

I think they have multiple users that need their data stored hence the arrays

can you give it in the example code because I'm kind of get it but kind of don't know where you mean point at@@

I can try but I am posting via iPhone try something like this

Code:

---

bool PlaceData(int );

int myarray[5000];

int main()
{
  // set all values of array to -1
  int value=0;
  while(value != -1)
  {
  cout<<"Enter a value: ";
  cin>>value;
  if(value != -1) PlaceData(value);
  }
  return 0;
}

bool PlaceData(int v)
{
  for(int i = 0; i < 5000;i++)
  {
      if(myarray[i] == -1)// open spot
      {
        myarray[i] = v;
        return true;
      }
  }
  return false;
}

---

Code:

---

#include <iostream>
#include <cstdlib>


using namespace std;
void Displaylab(int *lab,int size)
{
    int i;
    for(i = 0; i < size; i++)
    lab[i] = 0;
    lab[i] = -1;
    return;
}
int **dynArray(int row, int cols)
{
    int **myPtr;
    int lab[4];
    myPtr = new int *[row];
    for(int i = 0; i < row; i++)
    myPtr[i] = new int[lab[i]];
    int i = 0;
    int size;
    if(myPtr[i] == 0)
    cout<<"empty";
    return myPtr; 
}


void getinput(int ID,int &Station,int &labnumb)
{
    cout<<"Enter your ID number: "<<endl;
    cin>>ID;
      cout<<"Enter your station number: "<<endl;
    cin>>Station;
      cout<<"Enter your lab number: "<<endl;
    cin>>labnumb;
    return; 
}
void logout(int **Array,int ID,int row,int lab[])
{
    int r,c;
    if(search(**Array,ID,row,r,c,lab))    //Here is my mistake

    dynArray[r][c] = 0;                        //this one also.Need some help on debugging or fix it
    cout<< "You have been logged out."<<endl;
    return;
}
void login(int **Array,int ID,int &Station,int &labnumb)
{
    getinput(ID,Station,labnumb);
    Array[labnumb-1][Station-1] = ID; 
    return;
   
}
bool search(int **Array,int ID,int row,int &r,int &c,int lab[])
{
    cout<<"Enter user ID to check: "<<endl;
    cin>>ID;
    bool found = false;
    for(int i = 0; i < row;i++)
    for(int j = 0; j < lab[i];j++)
    if(ID == Array[i][j])
    {
      found = true;
      r = i;
      c = j;
     
      }
    return found;
}   


void Menu(int **Array,int ID,int &Station,int &labnumb,int row,int &r,int &c,int lab[])
{
    int choice;
    cout<<"Enter 1 for login, 2 for search,3 for exit. "<<endl;
    cin>>choice;
    if(choice == 1)
        login(Array,ID,Station,labnumb);
    if(choice == 2)
        search(Array,ID,row,r,c,lab);
    if(choice == 3)
        exit(0);
    return;
}


int main()
{
    int lab[4];
    lab[0] = 5;
    lab[1] = 6;
    lab[2] = 4;
    lab[3] = 3;
    int **labmain;
    labmain = new int*[4];
    for(int i = 0; i <4 ; i++)
    {
            *(labmain + i) = new int;
    }
    labmain = dynArray(4,7);
    int ID,Station,row,r,c,labnumb;
    Menu(labmain,ID,Station,labnumb,row,r,c,lab);
      system("PAUSE");
      return 0;
}

---

Here is my completing code but still with some mistake and i have tried a few days to debug it but I can't understand where that mistake get wrong

Are we storing rows and columns that they are sitting in as well?

Code:

---

C:\Users\David\Desktop\Cboard\eric\main.cpp||In function 'int** dynArray(int, int)':|                 
C:\Users\David\Desktop\Cboard\eric\main.cpp|22|warning: unused variable 'size'|                        You are not using the variable in the function why even declare it?
C:\Users\David\Desktop\Cboard\eric\main.cpp||In function 'void logout(int**, int, int, int*)':|
C:\Users\David\Desktop\Cboard\eric\main.cpp|42|error: 'search' was not declared in this scope|          Search is declared after the function you are using it in you can't do that.
C:\Users\David\Desktop\Cboard\eric\main.cpp|44|warning: pointer to a function used in arithmetic|          A pointer is not a value you want to use in arithmetic a pointer is likely not the same value you want to use
C:\Users\David\Desktop\Cboard\eric\main.cpp|44|warning: pointer to a function used in arithmetic|          Ditto
C:\Users\David\Desktop\Cboard\eric\main.cpp|44|error: assignment of read-only location '*(dynArray + (((unsigned int)r) + ((unsigned int)c)))'|              What is dynArray?  I don't even see it declared unless I am overlooking something.
C:\Users\David\Desktop\Cboard\eric\main.cpp|44|error: cannot convert 'int' to 'int**(int, int)' in assignment|
||=== Build finished: 3 errors, 3 warnings ===|

---

Hm... no really. Because In my search function i have search for the user login and save the position so that when I call function in the logout function it can search and logout the user forgot to logout

Code:

---

void logout(int **Array,int ID,int row,int lab[])
{
    int r,c;
    if(search(**Array,ID,row,r,c,lab))    //Here is my mistake
 
    dynArray[r][c] = 0;                        //this one also.Need some help on debugging or fix it
    cout<< "You have been logged out."<<endl;
    return;
}

---

when you call search you are not passing your array by using the double ** in the function call. Do keep that in mind.

Code:

---

dynArray[r][c] = 0;

---

Umm it is a function what are you trying to do call the function?

Maybe use:

Code:

---

dynArray(r,c) = 0;

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I wondering the second part I'm calling the position of the user login in the search function. And it isn't like this dynArray[][]= 0?

Code:

---

if(search(Array,ID,row,r,c,lab))

---

It still got the syntax error in no matching function call

Move search function declaration above the logout declaration.

It still doesn't work. The syntax error said non-value assismentT_T

OH, in that case:
Move the search function declaration above the logout declaration. Then post the updated code and actual copy-and-paste of the error message.

I see lots of new in your program, but no delete. Figure out how and when you are going to delete stuff and you will solve more of your problem.

Here is the new code with the non-lvalue in assignment

Code:

---

#include <iostream>#include <cstdlib>


using namespace std;
void Displaylab(int *lab,int size)
{
    int i;
    for(i = 0; i < size; i++)
    lab[i] = 0;
    lab[i] = -1;
    return;
}
int **dynArray(int row, int cols)
{
    int **myPtr;
    int lab[4];
    myPtr = new int *[row];
    for(int i = 0; i < row; i++)
    myPtr[i] = new int[lab[i]];
    int i = 0;
    int size;
    if(myPtr[i] == 0)
    cout<<"empty";
    return myPtr; 
}


void getinput(int ID,int &Station,int &labnumb)
{
    cout<<"Enter your ID number: "<<endl;
    cin>>ID;
      cout<<"Enter your station number: "<<endl;
    cin>>Station;
      cout<<"Enter your lab number: "<<endl;
    cin>>labnumb;
    return; 
}
void login(int **Array,int ID,int &Station,int &labnumb)
{
    getinput(ID,Station,labnumb);
    Array[labnumb-1][Station-1] = ID; 
    return;
   
}
bool search(int **Array,int ID,int row,int &r,int &c,int lab[])
{
    cout<<"Enter user ID to check: "<<endl;
    cin>>ID;
    bool found = false;
    for(int i = 0; i < row;i++)
    for(int j = 0; j < lab[i];j++)
    if(ID == Array[i][j])
    {
      found = true;
      r = i;
      c = j;
     
      }
    return found;
}   
void logout(int **Array,int ID,int row,int lab[])
{
    int r,c;
    if(search(Array,ID,row,r,c,lab))
    dynArray(r,c) = 0;
    cout<< "You have been logged out."<<endl;
    return;
}


void Menu(int **Array,int ID,int &Station,int &labnumb,int row,int &r,int &c,int lab[])
{
    int choice;
    cout<<"Enter 1 for login, 2 for search,3 for exit. "<<endl;
    cin>>choice;
    if(choice == 1)
        login(Array,ID,Station,labnumb);
    if(choice == 2)
        search(Array,ID,row,r,c,lab);
    if(choice == 3)
        exit(0);
    return;
}


int main()
{
    int lab[4];
    lab[0] = 5;
    lab[1] = 6;
    lab[2] = 4;
    lab[3] = 3;
    int **labmain;
    labmain = new int*[4];
    for(int i = 0; i <4 ; i++)
    {
            *(labmain + i) = new int;
    }
    labmain = dynArray(4,7);
    int ID,Station,row,r,c,labnumb;
    Menu(labmain,ID,Station,labnumb,row,r,c,lab);
      system("PAUSE");
      return 0;
}

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