Storing and printing matrices

This is a discussion on Storing and printing matrices within the C++ Programming forums, part of the General Programming Boards category; I am trying to make a program which will ask the user to input a series of numbers, then in ...

  1. #1
    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.

  2. #2
    Ethernal Noob
    Join Date
    Nov 2001
    Posts
    1,901
    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 08:05 AM.

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