916 Checkerboard V1 Codehs Fixed Review

If you’ve landed on this article, chances are you’re stuck on the "9.1.6 Checkerboard (v1)" problem in the CodeHS Java (or sometimes JavaScript Graphics) course. You’ve tried writing the code, but the checkerboard isn’t rendering correctly—maybe the colors are wrong, the rows aren’t alternating, or the squares aren’t aligned.

Don’t worry. This guide provides the complete, fixed solution and explains why each line of code exists, so you can pass the autograder and truly understand the concept.

function start()
    const SIZE = 50;
    for(let row = 0; row < 8; row++) 
        for(let col = 0; col < 8; col++) 
            let x = col * SIZE;
            let y = row * SIZE;
            let color = (row + col) % 2 === 0 ? "red" : "black";
            let rect = new Rectangle(SIZE, SIZE);
            rect.setPosition(x, y);
            rect.setColor(color);
            add(rect);

If you’re in JavaScript Graphics (Karel or similar), the standard checkerboard v1 problem wants you to:

Create an 8×8 checkerboard where alternating squares are red and black, starting with red in the top-left.

function start() 
    var size = 50;
    for (var i = 0; i < 8; i++) 
        for (var j = 0; j < 8; j++) 
            var rect = new Rectangle(size, size);
            rect.setPosition(j * size, i * size);
            if ((i + j) % 2 === 0) 
                rect.setColor("red");
             else 
                rect.setColor("black");
add(rect);

This will pass the 916 Checkerboard v1 CodeHS check.

Mastering the 916 Checkerboard v1: Solutions and Logic for CodeHS

If you are working through the CodeHS curriculum, you’ve likely encountered the 9.1.6 Checkerboard v1 assignment. It’s a classic challenge that tests your ability to use nested loops, coordinate systems, and conditional logic.

However, getting the "fixed" version—where the grid perfectly alternates colors without overlapping or skipping—can be tricky. The objective is to create an

grid of squares where the colors alternate between black and red (or other assigned colors), resembling a standard checkerboard. Key Technical Requirements:

Nested Loops: You need an outer loop for rows and an inner loop for columns.

Size Calculations: Each square must be the width of the canvas divided by 8.

The "Fixed" Logic: The color must switch based on both the row and column index to create the staggered effect. The Logic Behind the Fix

The most common mistake in "v1" is only checking if the column is even or odd. If you do that, every row will look identical, resulting in vertical stripes rather than a checkerboard. The Solution: Use the sum of the row and column indices. If (row + col) is even, color it Red. If (row + col) is odd, color it Black. The Corrected Code (JavaScript/Karel Style)

Here is a clean, "fixed" implementation for the CodeHS environment: javascript

var SQUARES_PER_SIDE = 8; var SQUARE_SIZE = getWidth() / SQUARES_PER_SIDE; function start() for (var row = 0; row < SQUARES_PER_SIDE; row++) for (var col = 0; col < SQUARES_PER_SIDE; col++) drawSquare(row, col); function drawSquare(row, col) var x = col * SQUARE_SIZE; var y = row * SQUARE_SIZE; var rect = new Rectangle(SQUARE_SIZE, SQUARE_SIZE); rect.setPosition(x, y); // The "Fixed" Logic: Check if sum of indices is even if ((row + col) % 2 == 0) rect.setColor(Color.red); else rect.setColor(Color.black); add(rect); Use code with caution. Troubleshooting Common Errors 1. The "Off-by-One" Pixel Gap

If you see white lines between your squares, ensure you are calculating SQUARE_SIZE using getWidth() / 8. If you hardcode a number like 50 on a canvas that isn't exactly 400, the grid won't fit perfectly. 2. Rectangles Overlapping the Border

Make sure your setPosition uses col * SQUARE_SIZE for the X-coordinate and row * SQUARE_SIZE for the Y-coordinate. Swapping these can sometimes cause the grid to render incorrectly if your canvas isn't a perfect square. 3. Infinite Loops

Ensure your for loop conditions use < SQUARES_PER_SIDE and not <=. Using <= will attempt to draw a 9th row/column, which usually breaks the layout or triggers a "limit exceeded" error in CodeHS. 916 checkerboard v1 codehs fixed

The "916 checkerboard v1 codehs fixed" solution relies entirely on the row + column parity. Once you master the nested loop structure, you can apply this logic to more complex grid-based games like Minesweeper or Chess.

Are you having trouble with the v2 version of this assignment, or is the autograder still giving you a specific error message?

Cracking the Code: How to Fix CodeHS 9.1.6 Checkerboard V1 If you're stuck on CodeHS 9.1.6: Checkerboard, v1

, you aren't alone. This exercise is a classic "gotcha" because it doesn't just want the right visual output; it wants you to use specific programming techniques—like nested loops and list indexing—to get there.

Many students fail this one because they try to "shortcut" the board creation by appending pre-made lists. Here’s how to fix your code so it passes every test case. The Problem: Why Your Code Isn't Passing The autograder for this exercise specifically checks for assignment statements

. If you just print strings or append a row of ones, you'll likely see errors like: "You should set some elements of your board to 1" "You will need to use an assignment statement"

The system wants to see you access a specific spot in a 2D list (e.g., board[i][j] = 1 The Solution: Step-by-Step Fix

To pass, you must first initialize a grid full of zeros and then use nested

loops to "spot-fill" the ones where the checker pieces should go. 1. Initialize the 8x8 Grid Start by creating a list of lists where every value is ): board.append([ Use code with caution. Copied to clipboard 2. Use Nested Loops with Assignment

Now, loop through the rows and columns. According to the instructions, you need 1s in the top three rows (indices 0, 1, 2) and the bottom three rows (indices 5, 6, 7). To get that alternating checkerboard look, use the modulus operator

). A common trick is checking if the sum of the row and column indices is even: (i + j) % 2 == 0 # Top 3 rows and Bottom 3 rows only : board[i][j] = # This is the "assignment statement" it wants! Use code with caution. Copied to clipboard 3. Print the Result Finally, call the provided print_board(board) function to display your work. Why This Version Works Nested Loops: It proves you can navigate a 2D data structure. board[i][j]

, you are directly modifying the data, which satisfies the "assignment statement" requirement.

statements correctly skip the middle two rows, leaving them as zeros.

Now that you've mastered the basic grid, are you ready to tackle Checkerboard v2 and add more complex patterns?

In the CodeHS 9.1.6 exercise, "Checkerboard v1," students must create an

grid using a 2D list and populate it with a specific pattern of 0s and 1s. The final result must be an

grid where the top three and bottom three rows are filled with 1s, and the middle two rows are filled with 0s. 1. Core Concept and Requirements If you’ve landed on this article, chances are

The objective is to practice manipulating 2D lists (lists of lists) by accessing specific indices and using assignment statements. The autograder typically requires: Initialization: Creating an grid starting with all 0s.

Nested Loops: Iterating through the grid to modify specific elements.

Assignment: Explicitly setting grid[i][j] = 1 for the required rows rather than just printing the final output. 2. Common Errors in Initial Attempts

Many users encounter a "red" error in the autograder stating: "You should set some elements of your board to 1; You will need to use an assignment statement.". This occurs because:

Formatting over Logic: Users might print a checkerboard pattern using a string or a simple print loop without actually updating the 2D list structure.

Function Scope: Defining the print_board function inside another function, making it inaccessible.

Incorrect Indexing: Failing to target exactly the top three (indices 0, 1, 2) and bottom three rows (indices 5, 6, 7). 3. The Fixed Solution Strategy

To fix the code and pass all CodeHS test cases, follow these structured steps: I. Initialize the 8x8 Grid

Create a 2D list containing eight sub-lists, each with eight zeros. grid = [] for i in range(8): grid.append([0] * 8) Use code with caution. Copied to clipboard II. Use Nested Loops for Assignment Iterate through every row ( ) and column (

). Use an if statement to check if the current row index is in the top three (less than 3) or bottom three (greater than 4). If it is, use an assignment statement to change the 0 to a 1.

for i in range(8): for j in range(8): if i < 3 or i > 4: grid[i][j] = 1 Use code with caution. Copied to clipboard III. Call the Print Function

Finally, pass your completed grid to the provided print_board function to display the result. Final Output Structure

The resulting 2D list represents a board where rows 0, 1, 2 and 5, 6, 7 are completely filled with 1s, creating the "v1" pattern required for the exercise.

916 Checkerboard V1 CodeHS Fixed: A Comprehensive Guide to Understanding and Implementing the Solution

The 916 Checkerboard V1 CodeHS is a popular coding challenge that has been making rounds in the programming community. As a coder, you're likely to have encountered this challenge at some point, and if you're reading this article, chances are you're looking for a fixed solution to the problem. In this article, we'll dive into the details of the 916 Checkerboard V1 CodeHS challenge, explore the issues that arise, and provide a fixed solution to help you overcome the obstacles.

What is the 916 Checkerboard V1 CodeHS Challenge?

The 916 Checkerboard V1 CodeHS challenge is a programming exercise that requires you to create a checkerboard pattern using a grid of squares. The challenge is designed to test your understanding of loops, conditionals, and functions in programming. The goal is to create a 8x8 grid with alternating black and white squares, resembling a traditional checkerboard. If you’re in JavaScript Graphics (Karel or similar)

Understanding the Requirements

Before we dive into the solution, let's break down the requirements of the challenge:

Common Issues with the 916 Checkerboard V1 CodeHS Challenge

Many coders struggle with the 916 Checkerboard V1 CodeHS challenge due to a variety of reasons. Some common issues include:

Fixed Solution: 916 Checkerboard V1 CodeHS

Here's a fixed solution to the 916 Checkerboard V1 CodeHS challenge:

function start() 
  var rows = 8;
  var cols = 8;
  var squareSize = 50;
for (var row = 0; row < rows; row++) 
    for (var col = 0; col < cols; col++) 
      var color = (row + col) % 2 == 0 ? "black" : "white";
      if (row == 0 && col == 0) 
        color = "black";
rect(col * squareSize, row * squareSize, squareSize, squareSize, color);

Explanation of the Solution

Let's break down the solution:

Tips and Variations

Here are some tips and variations to help you improve your solution:

Conclusion

The 916 Checkerboard V1 CodeHS challenge is a great opportunity to practice your programming skills, particularly with loops, conditionals, and functions. With this article, you now have a fixed solution to the challenge, along with a deeper understanding of the requirements and common issues that arise. Whether you're a beginner or an experienced coder, this challenge is a great way to improve your skills and learn new techniques. Happy coding!

This is the mathematical trick to the checkerboard pattern.

# Initialize the canvas
set_canvas_color(WHITE)
canvas_width = 800
canvas_height = 800
create_canvas(canvas_width, canvas_height)
# Define some colors
BLACK = (0, 0, 0)
WHITE = (255, 255, 255)
# Define the square size
square_size = canvas_width // 8
# Loop through each row
for row in range(8):
    # Loop through each column
    for col in range(8):
        # Calculate the color of the square
        if (row + col) % 2 == 0:
            fill(WHITE)
        else:
            fill(BLACK)
# Draw the square
        no_stroke()
        rect(col * square_size, row * square_size, square_size, square_size)

This solution uses a nested loop to iterate over each square on the checkerboard. The color of each square is determined by the sum of its row and column indices. If the sum is even, the square is white; otherwise, it is black.

The set_canvas_color and create_canvas functions are used to initialize the canvas with a white background. The rect function is used to draw each square, and the fill function is used to set the color of each square.

Before we jump to the "fixed" code, let’s break down the assignment’s requirements:

The most common "non-fixed" issues students encounter: