Thread: Help with making a custom checkerboard with nested loop

Hello, I'm trying to make a custom checkboard with given user input, in the form of (# of rows, # of columns, size of each square, filler character).
So the input 2 3 5 * would look like
*****.........*****
*****.........*****
*****.........*****
*****.........*****
*****.........*****
.........*****
.........*****
.........*****
.........*****
.........*****
I've made my loop, but I am unable to get more then a 1 1 1 checkerboard properly.
I am stuck on how to divide the filler characters to make the proper square size. As of now they are all one lined.

import java.util.*;
 
public class Checker{ 
 
public static void main(String[] args) {
int col, row, size; char filler;
System.out.println("Please enter 3 numbers and a character."); //output
Scanner scan = new Scanner(System.in); //input
 
row = scan.nextInt();
col = scan.nextInt();
size = scan.nextInt();
filler = scan.next().charAt(0);  // defined variables
 
int r,c,i=0,j=0,k=0;
 
for (r=1; r<=row; r++)
    {for (c=1; c<=col; c++)
        {do
 
            {   if ((r % 2 != 0 && c % 2 !=0) || (r %2 == 0 && c % 2 == 0))
                        { do {
                            System.out.print(filler);
                            i++;}
                            while (i<size);
                        	i = 0;
 
                        	}
 
 
                else { 
                          do
                          {  System.out.print(" ");
                              j++;}
                              while (j<size);
                              j = 0;
                     }
            k++;
            }while (k<size); 
        	k = 0;
 
        }System.out.println("\n");}
System.out.println("\nHave a nice day. Goodbye.");
 
}
}

You're also missing some simple math required to make the loops work. Your specification is a little confusing, but if you think it through, then the user's input

2 3 5 *

is a 2 x 3 checkerboard (row, column)
with a 5 x 5 sized square

So the number of rows is actually 2 squares * 5 rows / square or 10 rows. Then you'll have to divide those rows into 'blocks' so that the correct character is printed.

You'll need to do a similar calculation for the number of real columns.

@andbin: Now I understand why you suggested 4 loops. I was trying to figure out why so many were needed, but I was stuck in my own design idea, and I love the math.

Since I suggested it . . .

My approach:

- The size of the square defines the height or number of rows in a 'block' of output
- Each row in a block of output begins with the same character, either space for a 'white' square or the user's chosen character for a 'black' sqaure
- The block character being output alternates at the column block boundary

Logic (roughly)
Start the row with the correct character (outer loop)
Swap the character at each column block boundary (inner loop)
Swap the row character at the row block boundary

I've coded it, but it's not as efficient as I'd like it to be. In the end, the 4-loop approach may be inherently more efficient, but I haven't coded that one.

Really? Here's my for loop. Not that bad . . .

        for ( int i = 0 ; i < rows * squareSize ; i++ )
        {
            // start every row in the block with the same character
            if ( i % squareSize == 0 )
            {
                swapStartChar();
            }
 
            printChar = startChar;
 
            for ( int j = 0 ; j < columns * squareSize ; j++ )
            {
                if ( j % squareSize == 0 )
                {
                    swapPrintChar();
                }
 
                System.out.print( printChar );
            }
 
            System.out.println();
 
        }

I've fixed my loops, but still am unsure about how to go about the math. I get the general calculations, but I could do with some pointers on how and where to implement them. Thanks

Show what you done and describe what help you need. Post a sample run, too.