Question

I am trying to reverse this code so that I can print a diamond shape with a border around it. What is the best way to begin reversing a nested loop/series of loops? I tried tinkering around with the code but everything comes out jumbled and out of order. Any advice?

Also, is there a way to make an even number of .’s on each side of the stars at the top? The only way I have been able to make it work prints an even amount on each side by one…

Here is what should be printed to the console: https://i.stack.imgur.com/SyYzp.jpg

Here is my code:

public class SixTester {

    public static void main(String[] args)
    {
            int i,j,k;
            int numOfRows = 8;  // Made this a variable, so that the program can make any size diamond (try playing around with different values eg. 2 or 16)

            // Step 1. The first Dash
            for(i=0;i<numOfRows*2 +2;i++)
                    System.out.print(" "); // Number of spaces is double the number of rows in your 'Half Pyramid'
            System.out.println("-");

            // Step 2. The First half diamond
            for (j=0; j<numOfRows ; j++ )
            {
                    for(k=numOfRows*2; k>1+j*2; k--)
                            System.out.print(" ");

                    System.out.print("_/");
                    for (i=0; i< 2+j*4; i++)
                    {
                            // Prepare the Star rectangle, Note that it starts half the way (rows/2)
                            if(j >= numOfRows/2 && (i>j*2- numOfRows/2 && i<j*2+ numOfRows/2)) {
                                    System.out.print("*");                                 
                            }
                            else
                                    System.out.print(".");
                    }
                    System.out.println("\\_");
            }
            // Next Step  - Make the bottom pyramid...but how to reverse?
    }
}

Answer 1

This isn’t the most elegant way, but it works. Insert these lines where your code says “but how to reverse?” I’ve marked off the changes to your code with comments

        // COUNT BACKWARDS NOW. YOU WANT LARGEST ROW FIRST, OTHERWISE IT'S OK EXCEPT...
        for (j=numOfRows-1; j>=0 ; j-- ) 
        {
                for(k=numOfRows*2; k>1+j*2; k--)
                        System.out.print(" ");

                System.out.print("\\_"); // BORDERS ARE BACKWARDS. PUT BORDER ON OTHER SIDE
                for (i=0; i< 2+j*4; i++)
                {
                        if(j >= numOfRows/2 && (i>j*2- numOfRows/2 && i<j*2+ numOfRows/2)) {
                                System.out.print("*");                                 
                        }
                        else
                                System.out.print(".");
                }
                System.out.println("_/"); // PUT BORDER ON OTHER SIDE
        }

        for(i=0;i<numOfRows*2 +2;i++)
                System.out.print(" ");
        System.out.println("-");