Problem printing pyramid of asterisks recursively in UNIX system

[Kahlia]

Hi. I am trying to print a pyramid of asterisks using recursion so that the recursive function takes in an integer and prints that number of lines of asterisks and then reverses, eg:

 
   *   
  * *  
 * * *
* * * *
 * * *
  * *
   *
 

if you call print(4).

I understand the general idea and have managed to put together the following code.

void print(int n)
{
        if (n == 0)
        {
                return;
        }
        else
        {
                print(n-1);
                cout << '*' * n << endl;
        }
}
 

I realise I haven't provided the second half or the spaces as I was trying to get the asterisks printing first.

This source code compiles, however it prints:

42
84
126
168

which sounds like the ASCII codes multiplied by n. I'm guessing this is because when I am multiplying by an integer it converts the char to an integer as well.

Firstly, is there any way to stop this happening, and is there anyway to create the spaces without using a loop ?

Thanking anyone who responds.

[DumRat]

The problem is in this line :

cout << '*' * n << endl;
 

Here, '*' is of the type char, and n is of the type int. Now, when you say '*'*n, the result is taken as an int. That is, the ascii value of '*' is multiplied by n. That is why you get 42, 84.... (42 is the ascii of '*' I guess. )

What you have to do is print the '*' character n times. You can do it like this:

for(int i = 0; i < n; i++)
{
     cout << '* ';
} 
 

This will print one star and space for each iteration. You'd be able to enhance this to get the pattern you want.

[Kahlia]

Here, '*' is of the type char, and n is of the type int. Now, when you say '*'*n, the result is taken as an int. That is, the ascii value of '*' is multiplied by n. That is why you get 42, 84.... (42 is the ascii of '*' I guess. )

Yeah I'd figured that.

What you have to do is print the '*' character n times. You can do it like this:

for(int i = 0; i < n; i++)
{
     cout << '* ';
} 
 

This will print one star and space for each iteration. You'd be able to enhance this to get the pattern you want.

The problem I can see with doing it this way is that it uses iteration instead of recursion - I don't know how to implement the for loop inside a recursive function.

I have tried implementing the loop one way and got a warning:
warning: multi-character character constant
and it printed:

       10784
1078410784
10784
107841078410784
 10784
1078410784
10784
10784107841078410784
   10784
1078410784
10784
107841078410784
 10784
     10784

[DumRat]

A for loop can be inside a recursive function.
Anyway, do post your code.

[Kahlia]

The current code I have (not allowing for spaces) is:

 
#include <iostream>
 
using namespace std;
 
void print(int n);
 
int main()
{
        print(4);
 
        return 0;
}
 
void print(int n)
{
        if (n == 0)
        {
                return;
        }
        else
        {
                print(n-1);
                for (int i = 0; i < n; i++)
                        cout << "* ";
                cout << endl;
                print(n-1);
        }
}
 

which prints a very interesting pattern of stars, but not quite what I am after. I did realise that the problem with my multiple characters was that i had still used single quotation marks instead of changing to double quotation marks when adding the spaces.

It now prints

*
* *
*
* * *
*
* *
*
* * * *
*
* *
*
* * *
*
* *
*
 

[DumRat]

Work on it a little and I think you'd get the answer.