Storing and printing matrices

stevedawg85 · 03-19-2006, 02:21 PM

I am trying to make a program which will ask the user to input a series of numbers, then in end, display the numbers. I am using arrays and need to save the numbers in a 3x4 matrix and then display it. This is what I have:

Code:

#include <iostream>
#include <iomanip>
using namespace std;

const int numrow = 3;
const int numcol = 4;
	
int grades [numrow][numcol];

int main ()
{
	for (int i = 0; i <= 3; i++)
	{
	cout << endl;
	for (int j = 0; j <= 4; j++)
	{
	cout << "enter grades for row # " << (i + 1)<< ": ";
	cin >> grades [numrow][numcol];
	}
	}
            cout << setw (4) << grades [i][j];

	return 0;
}

any help would be greatly appreciated as I do not know what is missing/ needs to be put in/ needs to be changed/ etc.

indigo0086 · 03-20-2006, 08:57 AM

1) you should have the for loop control variables set to numrow and num col (i < numrow) (j < numcol) - (not i <= numrow since the last indice will always be one less than the size) - so you don't have to go back and change them when you change the size of the array

2)

Code:

cin >> grades [numrow][numcol];

You're resetting the same variable which is grades[3][4]. Which is out of the array boundaries. Remember the array of size three has elements [0][1][2].

3) Your'e outputting the Grades[i][j] outisde of the scope of where i and j were declared. You'd have to do another loop to output it.

Here's what I got.

Code:

#include <cstdlib>
#include <iostream>

using namespace std;

int main()
{
    const int numrow = 3;
    const int numcol = 4;
	
    int grades [numrow][numcol];

	for (int i = 0; i < numrow; i++)
	{   
	   cout << endl;
	   for (int j = 0; j < numcol; j++)
	   {
	       cout << "enter grades for row # " << (i + 1) << ": ";
	       cin >> grades [i][j];
	   }
	}	
    
    for (int i = 0; i < numrow; i++)
	{      
	   cout << endl;
	   for (int j = 0; j < numcol; j++)
	   {
	       cout << setw(4) << grades[i][j];
	   }
	}
	cout << endl;

    system("PAUSE");
    return 0;
}

03-19-2006, 02:21 PM	#1
stevedawg85 Registered User Join Date: Mar 2006 Posts: 36	Storing and printing matrices I am trying to make a program which will ask the user to input a series of numbers, then in end, display the numbers. I am using arrays and need to save the numbers in a 3x4 matrix and then display it. This is what I have: Code: #include <iostream> #include <iomanip> using namespace std; const int numrow = 3; const int numcol = 4; int grades [numrow][numcol]; int main () { for (int i = 0; i <= 3; i++) { cout << endl; for (int j = 0; j <= 4; j++) { cout << "enter grades for row # " << (i + 1)<< ": "; cin >> grades [numrow][numcol]; } } cout << setw (4) << grades [i][j]; return 0; } any help would be greatly appreciated as I do not know what is missing/ needs to be put in/ needs to be changed/ etc.
stevedawg85 is offline

03-20-2006, 08:57 AM	#2
indigo0086 Ethernal Noob Join Date: Nov 2001 Posts: 1,891	1) you should have the for loop control variables set to numrow and num col (i < numrow) (j < numcol) - (not i <= numrow since the last indice will always be one less than the size) - so you don't have to go back and change them when you change the size of the array 2) Code: cin >> grades [numrow][numcol]; You're resetting the same variable which is grades[3][4]. Which is out of the array boundaries. Remember the array of size three has elements [0][1][2]. 3) Your'e outputting the Grades[i][j] outisde of the scope of where i and j were declared. You'd have to do another loop to output it. Here's what I got. Code: #include <cstdlib> #include <iostream> using namespace std; int main() { const int numrow = 3; const int numcol = 4; int grades [numrow][numcol]; for (int i = 0; i < numrow; i++) { cout << endl; for (int j = 0; j < numcol; j++) { cout << "enter grades for row # " << (i + 1) << ": "; cin >> grades [i][j]; } } for (int i = 0; i < numrow; i++) { cout << endl; for (int j = 0; j < numcol; j++) { cout << setw(4) << grades[i][j]; } } cout << endl; system("PAUSE"); return 0; } Last edited by indigo0086; 03-20-2006 at 09:05 AM.
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