I'm sorry for asking this, but did anyone know what's the problem here?

Question

1.00/5 (3 votes)

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C++

#include <iostream>
#include <fstream>
using namespace std;
int main()
{
	ofstream myfile("Matrix.dat", ios::app);
	int A[100][100], B[100][100], mult[100][100], row1, co11, row2, co12, i, j, k;
	cout << "Enter no. of rows for matrix A: ";
	cin >> row1;
	cout << "Enter no. of columns for matrix A: ";
	cin >> co11;
	cout << "Enter no. columns for matrix B: ";
	cin >> row2;
	cout << "Enter no. of rows for matrix B: ";
	cin >> co12;

	myfile << row1 << endl;
	myfile << co11  << endl;
	myfile << row2  << co12 << endl;

	while  (co11 != row2)
	{
		cout << "sorry ! column  of  matric  a  is  not equal  to  row  matrix  b.";
		cout << "please enter rows and columns for a: ";
		cin  >> row1 >> co11;
		cout << "Please enter rows and column for the maxtrix B: ";
		cin >> row2 >> co12; }

	//read matrices
	//Storing elements of matrix A 
	cout << endl << "Enter elements of matrix A:" << endl;
	for (i = 0; i < row1; ++i)
		for (j = 0; j < co11; ++j)
		{
			cout << "Enter element A" << i + 1 << j + 1 << " : ";
			cin >> A[i][j];
		}

	//Storing elements of matrix B
	cout << endl << "Enter elements of matrix B:" << endl;
	for (i = 0; i < row2; ++i)
		for (j = 0; j < co12; ++j)
		{
			cout << "Enter element B" << i + 1 << j + 1 << " : ";
			cin >> B[i][j];

		}

	//Initialize the elements of matrices of multiplication to 0
	for (i = 0; i < row1; ++i)
		for (j = 0; j < co12; ++j)
			for (k = 0; k < co11; ++k)
			{
				mult[i][j] = 0;
			}
  
//Multiplication matrix A and B and storing in array mult
for(i = 0; i < row1; ++i)
for(j = 0; j < co12; ++j)
for(k = 0; k < co11; ++k)
{
  mult[i][j] +=  A[i][k] * B[k][j];
}

//Displaying the multiplication of two matrix
cout << endl << "Output Matrices: " << endl;
for(i = 0; i < row1; ++i)
for(j = 0; j < co12; ++j)

{
  cout << " " << mult[i][j];
  if(j == co12-1)
{
  cout << endl;
  myfile << endl;
}

                           
return 0;       
            

}
}

What I have tried:

i think there is a problem in the displaying part, but i don't know how to fix it. did i need to add or delete something on there? i tried so many times, but the output and the file doesn't give the correct output for the matrix multiplication.

This the ouput that I got from the code above :

Output Matrices :
19

This is the ouput that I got before I add myfile << endl and this what the ouput supposed to be :

Output Matrices :
19 22
43 50

So, I think there is something I need to fix on the display part of the code. But, I don't have any idea on how to fix it.

Posted 26-Apr-22 5:47am

sugeous

Updated 26-Apr-22 17:56pm

v4

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Comments

CHill60 26-Apr-22 11:49am

What makes you think there is a problem - describe the problem clearly

sugeous 26-Apr-22 11:58am

This what the output supposed to be after I compile and run it :

Output Matrices :
19 22
43 50

But, when I put the myfile << endl;, it showed the wrong ouput. So, I think there is something I need to fix on the display part of the code. But, I don't have any idea on how to fix it.

CHill60 26-Apr-22 12:06pm

If you want to be a coder you are going to have to learn to be more precise. " it showed the wrong ouput." What output did it show.
Use the Improve Question link to put these details into your original post

sugeous 27-Apr-22 0:00am

already improve my question, next time i will be more detail in asking the question. thank you ✨

Richard MacCutchan 26-Apr-22 12:17pm

In addition to providing clear information you need to use proper indentation of your code. As it stands that is difficult to read. Please reformat it so it is clear.

sugeous 27-Apr-22 0:02am

alright, thank you so much ✨

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OriginalGriff · Accepted Answer · 2022-04-26T06:13:00

Compiling does not mean your code is right! :laugh:
Think of the development process as writing an email: compiling successfully means that you wrote the email in the right language - English, rather than German for example - not that the email contained the message you wanted to send.

So now you enter the second stage of development (in reality it's the fourth or fifth, but you'll come to the earlier stages later): Testing and Debugging.

Start by looking at what it does do, and how that differs from what you wanted. This is important, because it give you information as to why it's doing it. For example, if a program is intended to let the user enter a number and it doubles it and prints the answer, then if the input / output was like this:

Input   Expected output    Actual output
  1            2                 1
  2            4                 4
  3            6                 9
  4            8                16

Then it's fairly obvious that the problem is with the bit which doubles it - it's not adding itself to itself, or multiplying it by 2, it's multiplying it by itself and returning the square of the input.
So with that, you can look at the code and it's obvious that it's somewhere here:

C++

int Double(int value)
   {
   return value * value;
   }

Once you have an idea what might be going wrong, start using the debugger to find out why. Put a breakpoint on the first line of the method, and run your app. When it reaches the breakpoint, the debugger will stop, and hand control over to you. You can now run your code line-by-line (called "single stepping") and look at (or even change) variable contents as necessary (heck, you can even change the code and try again if you need to).
Think about what each line in the code should do before you execute it, and compare that to what it actually did when you use the "Step over" button to execute each line in turn. Did it do what you expect? If so, move on to the next line.
If not, why not? How does it differ?
Hopefully, that should help you locate which part of that code has a problem, and what the problem is.
This is a skill, and it's one which is well worth developing as it helps you in the real world as well as in development. And like all skills, it only improves by use!

merano99 · Accepted Answer · 2022-04-26T10:22:00

As others have pointed out, there are problems with the indentation, the brackets, and then the return is in an awkward place in the code snippet.
You can save yourself the if query if you output the end of the line after the inner for loop.

C

//Displaying the multiplication of two matrix
cout << endl << "Output Matrices: " << endl;
for (i = 0; i < row1; ++i)
	for (j = 0; j < co12; ++j) 	{
		cout << " " << mult[i][j];
		if (j == co12 - 1)	{
			cout << endl;
			myfile << endl;
		}
		return 0;  <- wrong position
	}

I'm sorry for asking this, but did anyone know what's the problem here?

2 solutions

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