making table of LCM using arrays

azncrazycooler · #1 30-Nov-2005, 13:24

I am trying to make a table of LCM values using an array. I know that to find the LCM , you need the GCM. Im stuck in my program. Is it possible to call a function in a function? This is what I have so far. The table is set to 10 x 10. I currently have user input because it waits for the user to enter the row number and the column number for that specific LCM value. I.E 2x6, LCM is 6. Its currently got 4 errors, and im stuck and unsure hwo to fix them. Can someone help?

Code:

 
  CPP / C++ / C Code:
   #include <iostream>
using namespace std;
int findLCM(double, double);
int gcd(int, int);


void main()
{
	const int rowsize = 10;
	const int colsize = 10;
	
	int rowcount, colcount;
	int data[rowsize][colsize];
	
	// make muilt table
	for (int r = 0; r < rowsize; ++r)
	{
		for (int c = 0; c < colsize; ++c)
		{
			data[r][c]= findLCM(r,c);
		}
	}
	
	cout << " Enter number of rows to display: ";
	cin >> rowcount;
	cout << " Enter number of columns to display: ";
	cin >> colcount;
	

	// output table
	for (r = 0; r < rowcount; ++r)
	{
		for (int c = 0; c < colcount; ++c)
		{ 
			cout << data[r][c] << " ";
		}
		cout << endl;
	}

  
	double findLCM(double num, double num2)
	{
		double lcm;
		lcm = (num*num2)/gcd;
		return c;

	}

	
	
	int gcd(int n1, int n2)
	{
		while( 1 )
		{
			n1 = n1 % n2;
			if( n1 == 0 )
			return n2;
			n2 = n2 % n1;
			if( n2 == 0 )
			return n1;
		}
	}




}

Paramesh · #2 30-Nov-2005, 17:30

Hi azn,

Welcome to the GIDForums™.

First, dont confuse with parameters and return values.
For example, you have declared the findLCM statement like this:

CPP / C++ / C Code:

int findLCM(double, double);

But you are never passing a double to it.
Rather, the return value is double!

So, change that to

CPP / C++ / C Code:

double findLCM(int, int);

int all places.

Also, you have to declare the data array as double, since you are returning a double value.

Next, the error which comes here is this:
'r' : undeclared identifier in line 31
So, whats the error?
Because the compiler doesnt know where the variable r has been declared.
You have to declare it as int r, because of the scope problems.

Then, you have to define your functions findLCM, and gcd outside the main function.

The next error is in this line:

CPP / C++ / C Code:

		lcm = (num*num2)/gcd;

Because you should not pass the variables num1 and num2 to the gcd function.
It should be like this:

CPP / C++ / C Code:

		lcm = (num*num2)/gcd(num1, num2);

Can you understand why?

Again, in this function:

CPP / C++ / C Code:


	double findLCM(int num, int num2)
	{
		double lcm;
		lcm = (num*num2)/gcd;
		return c;
	}

What is the other error? Can you find that?

Now that all the syntax errors are gone, here comes the logical error:
Division by zero!!!
That is because you are passing 0 and 0 as the values to gcd function in the loop:

CPP / C++ / C Code:

for (int r = 0; r < rowsize; ++r)
	{
		for (int c = 0; c < colsize; ++c)
		{
			data[r][c]= findLCM(r,c);
		}
	}

You have to pass the values from 1 to <=colsize or rowsize.

Last but not the least, you have to define the main function as int main(), rather that void main. And you should return 0 to indicate successful execution:

CPP / C++ / C Code:

int main()
{
    // code.....

    return 0;
}

Regards,

Paramesh.

azncrazycooler · #3 30-Nov-2005, 21:05

Hello Paramesh.

Thank You for taking the time to take a look at my program. I've managed with your help to fix up all the errors from it. But one thing that confuses me is , some things that you suggested didint work. Is it because I am using visual basics?

Here is a copy of my code that works for me at least .

[edit] ohhhhh i just noticed theres a visual basics c++ section!!

CPP / C++ / C Code:

 #include <iostream>
using namespace std;
double findLCM (int, int);
int gcd(int, int);



void main()
{
	const int rowsize = 10;
	const int colsize = 10;
	
	int rowcount, colcount;
	int data[rowsize][colsize];
	
	// make muilt table
	for (int r = 1; r < rowsize; ++r)
	{
		for (int c = 1; c < colsize; ++c)
		{
			data[r][c]= findLCM(r,c);
		}
	}
	
	cout << " Enter number of rows to display: ";
	cin >> rowcount;
	cout << " Enter number of columns to display: ";
	cin >> colcount;
	

	// output table
	for (r = 1; r < rowcount; ++r)
	{
		for (int c = 1; c < colcount; ++c)
		{ 
			cout << data[r][c] << " ";
		}
		cout << endl;
	}

}
	
	double findLCM(int num, int num2)
	{
		int lcm;
		lcm = (num*num2)/gcd(num, num2);
		return lcm;

	}

	
	
	int gcd(int n1, int n2)
	{
		while( 1 )
		{
			n1 = n1 % n2;
			if( n1 == 0 )
			return n2;
			n2 = n2 % n1;
			if( n2 == 0 )
			return n1;
		}
	}

azncrazycooler · #4 30-Nov-2005, 22:36

I still need some help. My program has logical errors. For example wjen i enter 2 abd 3, the LCM is 6, but it shows the number before it. Cany someon help ?

WaltP · #5 01-Dec-2005, 02:02

Quote:

Originally Posted by azncrazycooler

I've managed with your [Paramesh's] help to fix up all the errors from it. But one thing that confuses me is , some things that you suggested didint work.

He pointed out many things. Can you be less vague?

Quote:

Originally Posted by azncrazycooler

Is it because I am using visual basics?

Doubtfully, since you are using (I assume) Visual C, not Visual Basic. VB is an entirely different language.

Quote:

Originally Posted by azncrazycooler

[edit] ohhhhh i just noticed theres a visual basics c++ section!!

No there isn't. We have a Visual C++ section. But that's for question related directly to extensions to C++ you'll find only in MS Visual C/C++ and MFC. Not for basic C++ programming questions like yours.

As for the code you just posted, it wouldn't compile. When I fixed the error it seemed to run perfectly for 10 by 10, although I didn't check all 100 answers. If there's a problem, you'll have to be more specific.

Show us the error, don't just tell us about it.

[edit]Oh, I see. When you enter 4 rows and 5 columns you get rows 1-3 and colums 1-4. Your description wasn't clear at all.

The answer has to do with loops. With that clue you should be able to find the problem.[/edit]

Paramesh · #6 01-Dec-2005, 03:52

Quote:

Originally Posted by azncrazycooler

But one thing that confuses me is , some things that you suggested didint work. Is it because I am using visual basics?

I too use Visual C++, and it worked for me.

Here we go:

For more simplification, remove all doubles in your code and convert them to int.

Did you read this:

Quote:

Originally Posted by Paramesh

Next, the error which comes here is this:
'r' : undeclared identifier in line 31
So, whats the error?
Because the compiler doesnt know where the variable r has been declared.
You have to declare it as int r, because of the scope problems.

It comes in the line:

CPP / C++ / C Code:

	for (r = 1; r < rowcount; ++r)
	{

So, you have to change r=1 to int r=1.

Again, when printing:

CPP / C++ / C Code:

	for (int r = 1; r < rowcount; ++r)
	{
		for (int c = 1; c < colcount; ++c)
		{ 
			cout << data[r][c] << " ";
		}
		cout << endl;
	}

You have to vary r from 1 to rowcount(i.e r <=rowcount)
Similarly, vary c from 1 to colcount.

At last:

Quote:

Originally Posted by Paramesh

Last but not the least, you have to define the main function as int main(), rather that void main. And you should return 0 to indicate successful execution:

CPP / C++ / C Code:

int main()
{
    // code.....

    return 0;
}

Paramesh.

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making table of LCM using arrays

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