Adding Two-Dimensional arrays together

Hey everyone, I'm having a little problem with adding two arrays together, as part of a Matrices program. Ive got the code for adding the matrices, I really dont think its right at all.

Here's the code

Code:

---

#include <cstdlib>
#include <iostream>
#include <string.h>

using namespace std;
int askselectioninput();
int main()
{
        cout<<"============================="<<endl;
        cout<<"|| Calculation of Matrices ||"<<endl;
        cout<<"============================="<<endl;
int numbers[3][4];
int row, col;
int option = 0;
int result =0;

for (row=1; !(row>3); row++)/
{ cout<<"Data for row: "<<row<<endl;
for (col=1; !(col>4); col++)
{ cout<<"Type a number: ";
cin>>numbers[row][col];
}
cout<<"Matrices Inserted.."<<endl;
}
while (true){

                option = askselectioninput();

                if (option ==1)
                {

                        cout<<"==================================="<<endl;
                        cout<<"||Addition of Current Matrices Data||"<<endl;
                        cout<<"==================================="<<endl;
                for (row=1; !(row>3); row++)
                {
        for (col=1; !(col>4); col++)
                  cout<<row + col<<" ";
  }
        cout<<"Results Successfully Displayed, returning to Main-Menu"<<endl<<endl<<endl;
                }

                else if (option ==2)
                {

                        cout<<"======================================"<<endl;
                        cout<<"||Subtraction of Current Matrices Data||"<<endl;
                        cout<<"======================================"<<endl;
                for (row=1; !(row>3); row++)
                {
        for (col=1; !(col>4); col++)
                  cout<<row - col<<" "<<endl;
  }
                }

                else if (option ==3)
                {
                        cout<<"==================================="<<endl;
                        cout<<"||Displaying Current Matrices Data||"<<endl;
                        cout<<"==================================="<<endl;
                        cout<<"The current results are: "<<endl;

        for (row=1; !(row>3); row++)
                {
        for (col=1; !(col>4); col++)
                { cout<<numbers[row][col]<<" ";
                }
                cout<<" "<<endl;
                }
        cout<<"Results Successfully Displayed, returning to Main-Menu"<<endl<<endl<<endl;
        }

                else if (option ==4)
                {
                        cout<<"==================================="<<endl;
                        cout<<"||Multiplying Current Matrices Data||"<<endl;
                        cout<<"==================================="<<endl;
                }
                else if (option ==5){
                        cout<<"--Program...TERMINATED--"<<endl;
                        cout<<"--I'll BE BACK--"<<endl;
                        exit (1);
                }

        }
}
int askselectioninput(){
        int option= 0;
        cout<<"==============YOUR TRANSACTION CHOICES==================="<<endl;
        cout<<"Press 1 for Addition              Press 2 for Subtraction"<<endl;
        cout<<"press 3 for Display Balance    Press 4 for Mutliplication"<<endl;
        cout<<"===============Press 5 for Quit=========================="<<endl;
        cin>>option;
        if (option >0 && option <6){
                return option;
        }

        else {
                cout<<"--Incorrect Value--"<<endl<<endl;
                return askselectioninput();
        }

}

---

P.S The rows and cols are meant to be 1 in this code

Code:

---

        for (row=1; !(row>3); row++)
                {
        for (col=1; !(col>4); col++)
  }

---

Quote:

---

Originally Posted by TBsparky

Hey everyone, I'm having a little problem with adding two arrays together, as part of a Matrices program. Ive got the code for adding the matrices, I really dont think its right at all.

---

1. What TWO arrays??? "numbers" and what else?
2. In C/C++ array index is zero-based. You are accessing array out-of-boundaries.
3. !(row>3) is customarily written as row <= 3;
4. you are NOT doing any addition, subtraction, etc.
5. Thank you for using code tags. However, there main porpose it to preserve proper indentation, which you do not have. Compare to this:

Code:

---


#include <cstdlib>
#include <iostream>
#include <string.h>

using namespace std;
int askselectioninput();
int main()
{
        cout<<"============================="<<endl;
        cout<<"|| Calculation of Matrices ||"<<endl;
        cout<<"============================="<<endl;
        //int numbers[3][4];
        int row, col;
        int option = 0;
        int result =0;
        int numbers[3][4];

        for (row=1; !(row>3); row++)
        {
                cout<<"Data for row: "<<row<<endl;
                for (col=1; !(col>4); col++)
                {
                        cout<<"Type a number: ";
                        cin>>numbers[row][col];
                }
                cout<<"Matrices Inserted.."<<endl;
        }
        while (true){

                option = askselectioninput();

                if (option ==1)
                {

                        cout<<"==================================="<<endl;
                        cout<<"||Addition of Current Matrices Data||"<<endl;
                        cout<<"==================================="<<endl;
                        for (row=1; !(row>3); row++)
                        {
                                for (col=1; !(col>4); col++)
                                        cout<<row + col<<" ";
                        }
                        cout<<"Results Successfully Displayed, returning to Main-Menu"<<endl<<endl<<endl;
                }

                else if (option ==2)
                {

                        cout<<"======================================"<<endl;
                        cout<<"||Subtraction of Current Matrices Data||"<<endl;
                        cout<<"======================================"<<endl;
                        for (row=1; !(row>3); row++)
                        {
                                for (col=1; !(col>4); col++)
                                        cout<<row - col<<" "<<endl;
                        }
                }

                else if (option ==3)
                {
                        cout<<"==================================="<<endl;
                        cout<<"||Displaying Current Matrices Data||"<<endl;
                        cout<<"==================================="<<endl;
                        cout<<"The current results are: "<<endl;

                        for (row=1; !(row>3); row++)
                        {
                                for (col=1; !(col>4); col++)
                                {
                                        cout<<numbers[row][col]<<" ";
                                }
                                cout<<" "<<endl;
                        }
                        cout<<"Results Successfully Displayed, returning to Main-Menu"<<endl<<endl<<endl;
                }

                else if (option ==4)
                {
                        cout<<"==================================="<<endl;
                        cout<<"||Multiplying Current Matrices Data||"<<endl;
                        cout<<"==================================="<<endl;
                }
                else if (option ==5)
                {
                        cout<<"--Program...TERMINATED--"<<endl;
                        cout<<"--I'll BE BACK--"<<endl;
                        exit (1);
                }

        }
}
int askselectioninput(){
        int option= 0;
        cout<<"==============YOUR TRANSACTION CHOICES==================="<<endl;
        cout<<"Press 1 for Addition              Press 2 for Subtraction"<<endl;
        cout<<"press 3 for Display Balance    Press 4 for Mutliplication"<<endl;
        cout<<"===============Press 5 for Quit=========================="<<endl;
        cin>>option;
        if (option >0 && option <6){
                return option;
        }

        else {
                cout<<"--Incorrect Value--"<<endl<<endl;
                return askselectioninput();
        }

}
//P.S The rows and cols are meant to be 1 in this code

---

Quote:

---

1. What TWO arrays??? "numbers" and what else?
2. In C/C++ array index is zero-based. You are accessing array out-of-boundaries.
3. !(row>3) is customarily written as row <= 3;
4. you are NOT doing any addition, subtraction, etc.
5. Thank you for using code tags. However, there main porpose it to preserve proper indentation, which you do not have. Compare to this:

---

1. the two arrays are numbers [3] [4] for the rows and columns to which i have to calculate together.

2. I'm sorry but the for loop code, for the rows and cols, is what the lecturer had posted for us to use, When i set it to 0 is messes the whole program up.

3. I dont quite get what your saying with this one

4. The reason for THIS program is preform addition, subtraction and multiplication on two dimensional arrays for matrices

Quote:

---

Originally Posted by TBsparky

1. the two arrays are numbers [3] [4] for the rows and columns to which i have to calculate together.

---

What? I don't understand what you're saying here.

Quote:

---

2. I'm sorry but the for loop code, for the rows and cols, is what the lecturer had posted for us to use, When i set it to 0 is messes the whole program up.

---

Put simply, your row for loop will attempt to access numbers at numbers[1][*], numbers[2][*], and numbers[3][*] (where * doesn't matter). However, 3 is an invalid index for the first dimension of numbers-----valid indexes are 0, 1, and 2. Trying to access 3 is simply wrong, so you either misunderstood your lecturer, or he's teaching you incorrect information and you need to get out of that class immediately.

Sorry let me explain. The two arrays being used are numbers [3] [4]
which are initialized in the for loop when in the:

"cin>>numbers[row][col]"

So rows is array [3] and cols is array [4]

I Hope it clears it up.

Also the whole variables, for loop and int row,col
is the code she provided as a base line to work from.

Sorry but i don't quite understand, the code works, as far as i know, when entering data in the rows and cols, meaning it displays in the form of matrices. I'm not saying your wrong its just would i need to change it if it seems to work? Minus the addition code of course which i need to add.

Quote:

---

Originally Posted by TBsparky

1. the two arrays are numbers [3] [4] for the rows and columns to which i have to calculate together.

---

"numbers[3][4]" is ONE two-dimencional array (matrix).
Check this out.

Quote:

---

Originally Posted by TBsparky

2. I'm sorry but the for loop code, for the rows and cols, is what the lecturer had posted for us to use, When i set it to 0 is messes the whole program up.

---

Well, for numbers[3][4], there is NO element numbers[3][4].

Quote:

---

Originally Posted by TBsparky

3. I dont quite get what your saying with this one

---

I am saying that instead of "if NOT (row GREATER THEN 3)" people usually say "if (row LESS_THAN_OR_EQUAL_TO 3)". Just a matter of taste, I guess.

Quote:

---

Originally Posted by TBsparky

4. The reason for THIS program is preform addition, subtraction and multiplication on two dimensional arrays for matrices

---

But your code:

Code:

---

cout<<row + col<<" ";

---

doesn't add anything; it simply outputs current row index + current column index, which makes no sense at all.

Code:

---

cout<<row + col<<" ";

---

doesn't add anything; it simply outputs current row index + current column index, which makes no sense at all.[/QUOTE]

but when the program runs it asks for input, to put into the array and then it brings up a prompt, from the bottom of the program,

Code:

---


int askselectioninput(){
        int option= 0;

        cout<<"==============YOUR TRANSACTION CHOICES==================="<<endl;
        cout<<"Press 1 for Addition              Press 2 for Subtraction"<<endl;
        cout<<"press 3 for Display Balance    Press 4 for Mutliplication"<<endl;
        cout<<"===============Press 5 for Quit=========================="<<endl;
        cin>>option;
        if (option >0 && option <6){
                return option;
        }

        else {
                cout<<"--Incorrect Value--"<<endl<<endl;
                return askselectioninput();
       
}

}

---

This prompt is where it asks for the options to which i need to work out the addition code as i know the rest of my program worls.

Numbers is not 2 different arrays though....it's a single 2D array with 3*4=12 elements. When you talk about "adding" there's usually 2 things to work with, not just 1. Hence the confusion.

Quote:

---

Sorry but i don't quite understand, the code works, as far as i know, when entering data in the rows and cols, meaning it displays in the form of matrices. I'm not saying your wrong its just would i need to change it if it seems to work? Minus the addition code of course which i need to add.

---

C++ doesn't offer any guarantees that doing incorrect things will cause the program to crash or not build. However, if you make an out-of-bounds access, then you're either reading or writing memory which does not really belong to the variable you think you're accessing. This is a major problem since it can either crash your program or----much worse----result in subtle corruptions to other variables which you don't notice immediately. These latter types of bugs can be much more difficult to track down than a simple crash.

I'll say again, if your professor doesn't know that C and C++ use array indexes from 0 to N-1 rather than 1 to N, then he doesn't know one of the most fundamental aspects of the language and has no business teaching it.

I think I might have the program wrong.. It's a Matrices program that calculates ONE 2D Array of rows and columns together to display a final Matrices.

So you think if i change the values to 1 it would solve one problem. Also, is my addition code right at all?

Perhaps you should show us the instructions for the assignment, I'm still not understanding the purpose.

Quote:

---

Originally Posted by TBsparky

.. It's a Matrices program that calculates ONE 2D Array of rows and columns together to display a final Matrices.

---

Sorry, but I can't understand what you are saying here.
Anybody want to take over?

Quote:

---

Assignment 2, part 1
Using one of the following development environments:
 Microsoft Visual Basic 2005/2008/2010
 Microsoft Visual C++ Console Application
 Netbeans C++ Console Application
Task (50&#37; of the grade for this assignment – up to C8)
 Write a program to solve a pair of simultaneous equations for 2 unknowns: x and y. Where the coefficients of x and y may be represented as a 2x2 matrix.
 Where possible, efficient use should be made of appropriate programming and data structures (e.g. loops and arrays).
 If a solution is not possible, an appropriate message should be displayed to the user.
Note:
 Part 2 of this assignment will be held in-class on 12th May and will also contribute the remaining 50% of the grade for this assignment.
 Part 2 of this assignment will be based on the identification of appropriate test data and expected results for the program submitted in Part 1
VB – A possible interface:
C++ – A possible interface:
VB – Submission:
C++ - Submission:
Zipped project folder .cpp file
Grading Criteria:
 Programs should be well-structured using an appropriate interface. However, no credit will be given for unnecessary use of colours, fonts etc. in VB projects.
 Programs should be well-structured using appropriate

Here is the 2D Array for C++ VB will be posted at a later date.

Code:

---

#include <iostream>
using namespace std;
void main()
{ /* declare variables */
int numbers[3][4];
int row, col;
/* inputs */
for (row=1; !(row>3); row++)
{ cout<<"Data for row: "<<row<<endl;
for (col=1; !(col>4); col++)
{ cout<<"Type a number: ";
cin>>numbers[row][col];
}
cout<<endl;
}
/* outputs */
for (row=1; !(row>3); row++)
{
for (col=1; !(col>4); col++)
{ cout<<numbers[row][col]<<" ";
}
cout<<"End"<<endl;
}
}

---

---

she has also posted the 1D Array

Code:

---

1-D Arrays in C++
#include <iostream>
using namespace std;
void main()
{ /* declare variables */
int values[10];
int i;
/* inputs */
for (i=0; i<10; i++)
{cout<<"Type a number: ";
cin>>values[i];
}
/* outputs */
for (i=0; i<10; i++)
cout<<values[i]<<endl;
}

---

Quote:

---

Write a program to solve a pair of simultaneous equations for 2 unknowns: x and y. Where the coefficients of x and y may be represented as a 2x2 matrix.

---

Here's the relevant bit. Before you worry too much about how to write the code, have you figured out the exact sequence of steps you would need to do by hand to solve this problem?

By the exact sequence of steps you mean how the program will input, calculate and display?

No, I mean, given that someone hands you a paper with the coefficients of 2 equations written on it, do you know how to solve for x and y. You can't write a program to do this unless you know how to do it by hand.

Oh yes I can calculate simultaneous equations by hand. I just found it difficult using a loop to attempt to calculate them with like addition. I just don't understand the whole calculation via a loop with a 2D Array of [3] [4]. I'm a total noob at C++. I've tried an attempt and to me it doesn't seem correct.

Please, lay out the sequence of steps you'd use to solve this pair of equations, and we'll go from there.

9 = 4x + 6y
-3 = x - 10y

Quote:

---

Originally Posted by TBsparky

Oh yes I can calculate simultaneous equations by hand.

---

The issue is how you are solving these by hand. If you're solving them by hand using the algrebaic way of doing things, you will be here for months writing a program to simulate what you learned in junior high school. Heck, an expert would be here for weeks writing such a program.

The easiest way that simultaneous equations are solved by computer is to use Gaussian elimination. Did your teacher discuss that? If not, please look that up, as you cannot possibly write a program to solve equations in the "traditional" math book way.

Regards,

Paul McKenzie

No she did not discuss the Gaussain method. As far as i know its Solving Simultaneous equations by the use of matrices

Quote:

---

Originally Posted by TBsparky

by the use of matrices

---

Key phrase. Do you know what this means? "use of matrices" can mean anything.

Quote:

---

Originally Posted by TBsparky

No she did not discuss the Gaussain method. As far as i know its Solving Simultaneous equations by the use of matrices

---

And Guassian method uses matrices.

Again, you cannot write a program within a reasonable time trying to solve equations the way you do by hand using traditional math. The routine you want is called Guassian elimination. Just do a google search, and you will see the routine explained to you.

If your teacher wants you to solve equations as you do with traditional math you learned in school, he or she is playing a very cruel joke on you. You won't, and I bet your entire class won't be able to complete the assignment, or even know where to start if that is really what the teacher is expecting. So I'm assuming your teacher is wanting you to solve the equations using Gaussian elimination (there are other methods, but this is the easiest to implement).

Edit:

Here is a link to a previous topic. Please read:

http://www.codeguru.com/forum/showth...light=gaussian

Regards,

Paul McKenzie

Quote:

---

Originally Posted by Paul McKenzie

Again, you cannot write a program within a reasonable time trying to solve equations the way you do by hand using traditional math.

---

You can actually, for this specific case: 2 equations in 2 unknowns. It's simple enough in that case to write out the substitutions explicitly.

Gaussian elimination is the more general solution for handling n equations in n unknowns, of course.