def print_board(board): for i in range(len(board)): print(" ".join([str(x) for x in board[i]]))
: In Python, all code within the checkerboard function must be indented properly to execute as a single block.
: Avoid manually typing out the lists; the challenge expects you to use loops to generate the pattern programmatically.
) is even or odd. If the sum is even, use Color A; if odd, use Color B. Step-by-Step Implementation 1. Define Constants
If (row + column) % 2 == 0 → Color A. If (row + column) % 2 == 1 → Color B. 9.1.7 Checkerboard V2 Codehs
To successfully implement the checkerboard programmatically, you must understand two core concepts: 1. 2D Lists (Grid Matrix)
At first glance, this problem seems simple: draw a checkerboard. But the "V2" designation introduces specific logic constraints that often trip up students. This article will break down the problem, explain the underlying logic of nested loops and modulus operators, provide step-by-step code solutions in both Java and JavaScript, and offer debugging tips to help you pass the autograder on your first attempt.
def build_fancy_checkerboard(rows, cols, char_a='X', char_b='O'): board = [] for i in range(rows): row = [] for j in range(cols): if (i + j) % 2 == 0: row.append(char_a) else: row.append(char_b) board.append(row) return board
The exercise is a rite of passage in CodeHS. It transitions you from writing linear code to thinking in two dimensions. By mastering the nested loop and the modulo operator ( % ), you gain the tools necessary to build more complex graphics and data structures in the future. Need help with a specific part of the code, or If the sum is even, use Color A; if odd, use Color B
: If you add the row index and the column index together ( r + c ), the resulting sum alternates between even and odd numbers across the entire grid.
This essay explores the logic and implementation of the Checkerboard V2 challenge in the CodeHS 9.1.7 curriculum
When submitting your code to the CodeHS autograder, small logical errors can cause tests to fail. Watch out for these three common mistakes:
Building the program in CodeHS is all about mastering nested loops and using the modulo operator ( % ) to alternate colors efficiently. If (row + column) % 2 == 1 → Color B
The iterates through the columns of the current row. 3. Apply the Modulo Condition
In some versions, V2 also requires that you use a to track color state, rather than just checking (row + col) % 2 .
We create an empty list named board . Then, we use a loop to append 8 empty row lists.
The "9.1.7 Checkerboard, v2" challenge is an important building block. By understanding how to construct and display a 2D list using loops and conditional logic, you are gaining skills that are essential for more advanced programming, such as building games like Tic Tac Toe, Grid, and other applications that rely on a 2D coordinate system.