Question

How can I output the below asterisks in rhombus shape in c++ using the least number of loops and variables. Maximum no. of stars = n (input taken from the user)

  *
 * *
* * * = n
 * * 
  *

I tried doing it with just 2 loops but didn’t succeed plus the program is too complicated to understand so didn’t include it here.

So any algorithms you can think of?

Answer 1

This is a common question for education I believe, and thus a Google search is very helpful.

Here is a ready made solution in Visual C++ (as some people learn better from code examples, the choice is yours)…

http://www.softwareandfinance.com/Visual_CPP/Loops_Diamond_Pattern.html

EDIT: Trying to reduce the for loops and keeping the spacing between stars, this is my best effort…

int i, j;
int n = 0;
std::cout << "Enter the maximum number of *:";
std::cin >> n;

std::cout << "\n\n";

for (i = 1; i <= n; i++)
{
      std::cout.width(n - i);
      std::cout.fill(' ');
      std::cout << "";

      for (j = 1; j <= i; j++)
            std::cout << "* ";

      std::cout.width(n - i);
      std::cout.fill(' ');
      std::cout << "";

      std::cout << "\n";
}

for (i = n - 1; i >= 1; i--)
{
      std::cout.width(n - i);
      std::cout.fill(' ');
      std::cout << "";

      for (j = 1; j <= i; j++)
            std::cout << "* ";

      std::cout.width(n - i);
      std::cout.fill(' ');
      std::cout << "";

      std::cout << "\n";
}

std::cout << "\n";

ONLY 2 LOOPS USED:

int i, j;
int n = 0, c = 0, inc = 1;
std::cout << "Enter the maximum number of *:";
std::cin >> n;

std::cout <<"\n\n";

for (i = 1; i <= (n * 2) - 1; i++)
{
    c += inc;
    if(i == n)
        inc = -1;

    std::cout.width(n - c);
    std::cout.fill(' ');
    std::cout << "";

    for (j = 1; j <= c; j++)
        std::cout << "* ";

    std::cout.width(n - c);
    std::cout.fill(' ');
    std::cout << "";

    std::cout <<"\n";
}

std::cout <<"\n";