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Feb 11th, 2008

Trying to create a 2D array

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im trying to create a 2D array using a random generator but the compiler keeps giving me compiling error no matter how i modify the calling function

C++ Syntax (Toggle Plain Text)
#include <iostream>
#include <ctime>
 
using namespace std;
 
const int MAX = 4;
 
void constructArray (int a [][MAX], int);
 
 
int main()
{
	int a [MAX];
 
	srand (time (NULL));
 
	constructArray (a [][MAX], MAX);
 
 
 
}
 
void constructArray (int a [][], int size)
{
	for (int i = 0; i < size; i++)
		a [i][size] = rand () % 10;
}
#include <iostream>
#include <ctime>

using namespace std;

const int MAX = 4;

void constructArray (int a [][MAX], int);


int main()
{
	int a [MAX];
	
	srand (time (NULL));
	
	constructArray (a [][MAX], MAX);

	
	
}

void constructArray (int a [][], int size)
{
	for (int i = 0; i < size; i++)
		a [i][size] = rand () % 10;
}

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number87

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Feb 11th, 2008

Re: Trying to create a 2D array

As it is only 3 lines of code do you need a function?

C++ Syntax (Toggle Plain Text)
const int MAXROW = 4;
const int MAXCOL = 10;
 
int main()
{
  int a [MAXROW][MAXCOL];
  for (int row = 0; row < MAXROW; row++)
    for (int col = 0; col < MAXCOL; col++)
      a[row][col] = rand () % 10;
}
const int MAXROW = 4;
const int MAXCOL = 10;

int main()
{
  int a [MAXROW][MAXCOL];
  for (int row = 0; row < MAXROW; row++)
    for (int col = 0; col < MAXCOL; col++)
      a[row][col] = rand () % 10;
}

Passmark

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Feb 11th, 2008

Re: Trying to create a 2D array

And array cannot contain 2 empty dimensions in a function. You must fill in at least the left dimension.

WaltP

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Feb 11th, 2008

Re: Trying to create a 2D array

oh i used a function coz the array would be part of a larger program....

so...if i wanna print the array on screen now...i added in a few more lines....but the compiler gives me an error msg at line 21....
whats wrong there? i filled up both dimensions of the array, why cant it work?

(Toggle Plain Text)

#include <iostream>
using namespace std;

const int MAXROW = 4;
const int MAXCOL = 10;



int main()
{
  srand(time(NULL));
  
  int a [MAXROW][MAXCOL];
  
  for (int row = 0; row < MAXROW; row++)
  {  
    for (int col = 0; col < MAXCOL; col++)
      {
             a[row][col] = rand () % 10;
      }
  cout << a[row][col] << "\t";
  cout << endl;
  }    
  

}

number87

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Feb 11th, 2008

Re: Trying to create a 2D array

Click to Expand / Collapse Quote originally posted by number87 ...

gives me an error msg at line 21....

You've declared 'col' inside the inner for loop. That means that when the loop is done, col is outside of scope.
To solve this problem you would have declare 'int col' in the same scope as where you use it. So right after this line : int a [MAXROW][MAXCOL]; for example. Just put a int col = 0; after it, and remove the 'int' delcaration from the for loop
:

c Syntax (Toggle Plain Text)
#include <iostream>
#include <time.h>
using namespace std;
 
const int MAXROW = 4;
const int MAXCOL = 10;
 
 
 
int main()
{
	srand(time(NULL));
 
	int a [MAXROW][MAXCOL];
	int col=0 ,row =0;
 
	for (row = 0; row < MAXROW; row++)
	{ 
		for (col = 0; col < MAXCOL; col++)
		{
			a[row][col] = rand () % 10;
		}
		cout << a[row][col] << "\t";
		cout << endl;
	} 
 
        return 0;
}
#include <iostream>
#include <time.h>
using namespace std;

const int MAXROW = 4;
const int MAXCOL = 10;



int main()
{
	srand(time(NULL));

	int a [MAXROW][MAXCOL];
	int col=0 ,row =0;

	for (row = 0; row < MAXROW; row++)
	{ 
		for (col = 0; col < MAXCOL; col++)
		{
			a[row][col] = rand () % 10;
		}
		cout << a[row][col] << "\t";
		cout << endl;
	} 

        return 0;
}

Please note the return 0; at the end of the program.
I didn't check your logic, so the program may not give you the correct output.

Last edited by Nick Evan; Mar 26th, 2010 at 9:00 am.

Nick Evan

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Feb 11th, 2008

Re: Trying to create a 2D array

If you want to display the entire 'matrix' you might want to move line 23: cout << a[row][col] << "\t"; inside thee 'for'loop. (on line 21)

Last edited by Nick Evan; Mar 26th, 2010 at 9:00 am.

Nick Evan

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