Filling 2d array with alphanumeric characters

[gl3nnn]

So my code below compiles. However, whenever the console window pops out it just crashes. Is there something wrong with my code, particularly at the getRandom function.

 #include <iostream>
#include <cstdlib>
#include <ctime>
using namespace std;

const int MAX = 100;

//Function for rows and columns
void getRowColumn(int&, int&);

//Function to return values
char getRandom(int);

//Function to construct 2D array
void construct2D(char[][MAX], int, int, int);

//Function to print 2D array
void print2D(const char [][MAX], int, int, int);

int main()
{
	char str[MAX][MAX];
	int rows, columns;
	int k;
	
	
	srand(time (NULL));
	getRandom(k);
	construct2D(str, rows, columns, k);
	print2D(str, rows, columns, k);
}


void getRowColumn(int& rows, int& columns)
{
	
	rows = rand() % 7 + 4;
	columns = rand() % 7 + 4;
	

}


char getRandom(int k)
{
	
	const char alphaNumeric [] = 
	"0123456789"					  	 
	"ABCDEFGHIJKLMNOPQRSTUVWXYZ"
	"abcdefghijklmnopqrstuvwxyz";
	
	k = sizeof(alphaNumeric) - 1;
	
	return alphaNumeric[rand() % k];
	
}


void construct2D(char str[][MAX], int rows, int columns, int k)
{
	
	
	for (int i = 0; i < rows; i++)
	{
		for (int j = 0; j < columns; j++)
		{
			str [i][j] = k;	   	   
		}
	}

}


void print2D(const char str [][MAX], int rows, int columns, int k)
{
	for (int i = 0; i < rows; i++)
	{
		for (int j = 0; j < columns; j++)
		{
			cout << str [i][j] << "     ";	  	  
		}
		
		cout << endl;
	}
	
}

[coder777]

The problem with getRandom(...) is that you pass k as a copy not as a reference. Thus in main k remains uninitialized. It does not make sense to pass k to construct2D(...)/print2D(...).

In order to initialize str with different letters you should assign the result of getRandom() on line 67.

Further more rows/columns remain uninitialized because you don't call getRowColumn(...).

[lastchance]

getRandom is passed a parameter k (which you haven't defined beforehand, and which won't get passed back after being set in getRandom unless you make it a reference parameter by preceding it by & in the function header). Your code crashes because after your call to getRandom you try to use an undefined k in other routines.

On the other hand, getRandom returns a char, which you don't do anything with. TBH, it's not clear what you are trying to do.

[coder777]

lastchance wrote:

Your code crashes because after your call to getRandom you try to use an undefined k in other routines.

No, that's not the reason. See my post above: It's the uninitialzed rows/columns.

[lastchance]

Thanks for the correction, coder777

Was this what was intended? The passing of k between routines has been removed. (Coder777 was right - it was unnecessary, but not the cause of the crash) and the call to getRandom in main is replaced by getRowColumn(...).

#include <iostream>
#include <cstdlib>
#include <ctime>
using namespace std;

const int MAX = 100;

//Function for rows and columns
void getRowColumn(int&, int&);

//Function to return values
char getRandom(int);

//Function to construct 2D array
void construct2D(char[][MAX], int, int );       // Last parameter removed

//Function to print 2D array
void print2D(const char [][MAX], int, int );     // Last parameter removed

int main()
{
	char str[MAX][MAX];
	int rows, columns;
	int k;
	
	
	srand(time (NULL));
	getRowColumn( rows, columns );            // Was this what you wanted?
	construct2D(str, rows, columns);          // No k needed
	print2D(str, rows, columns );             // No k needed
}


void getRowColumn(int& rows, int& columns)
{
	
	rows = rand() % 7 + 4;
	columns = rand() % 7 + 4;
	

}


char getRandom()                                  // No parameter needed
{
	int k;                                     // but still have to declare k
	const char alphaNumeric [] = 
	"0123456789"					  	 
	"ABCDEFGHIJKLMNOPQRSTUVWXYZ"
	"abcdefghijklmnopqrstuvwxyz";
	
	k = sizeof(alphaNumeric) - 1;
	
	return alphaNumeric[rand() % k];
	
}


void construct2D(char str[][MAX], int rows, int columns )     // No k needed
{
	
	
	for (int i = 0; i < rows; i++)
	{
		for (int j = 0; j < columns; j++)
		{
			str [i][j] = getRandom();              // As per Coder777's suggestion	   	   
		}
	}

}


void print2D(const char str [][MAX], int rows, int columns )   // No k needed
{
	for (int i = 0; i < rows; i++)
	{
		for (int j = 0; j < columns; j++)
		{
			cout << str [i][j] << "     ";	  	  
		}
		
		cout << endl;
	}
	
}