Karel always starts facing East at (1,1) .
var WIDTH = 400; // 400 / 8 = 50px per square (perfect) var ROWS = 8; var squareSize = WIDTH / ROWS; // Results in integer 50
: Using getWidth() / DIAMETER ensures that your checkerboard fills the screen regardless of how big the canvas is. Pro-Tip for CodeHS Debugging 916 checkerboard v1 codehs fixed
For Karel-based versions, the robot must move across the grid while painting alternating colors:
Mastering CodeHS 9.1.6: Fixed Checkerboard V1 The CodeHS Exercises 9.1.6 (often stylized as 9.1.6 Checkerboard v1) tasks programmers with creating a grid pattern using standard control structures. A common pitfall in this challenge involves logic errors that cause the checkerboard pattern to offset incorrectly, skip spaces, or throw out-of-bounds exceptions. Karel always starts facing East at (1,1)
function main() while(leftIsClear()) fillRow(); repositionToNextRow(); fillRow(); // Fills the very last row // Function to fill a single row with alternating checkers function fillRow() putBeeper(); while(frontIsClear()) move(); if(frontIsClear()) move(); putBeeper(); // Function to handle moving to the next row and switching direction function repositionToNextRow() if(facingEast()) turnLeft(); if(frontIsClear()) move(); turnLeft(); else turnRight(); if(frontIsClear()) move(); turnRight(); // Helper function to turn right function turnRight() turnLeft(); turnLeft(); turnLeft(); Use code with caution. Detailed Breakdown of the Fixed Code
To fix the CodeHS exercise, the key is not just printing the right visual output, but correctly modifying a list of lists using nested for loops and assignment statements . The Correct Logic A common pitfall in this challenge involves logic
This is where most students run into errors. Standard buggy code often tries to alternate elements by flipping a boolean flag after every iteration. However, flag-flipping breaks down when a row ends, because the first cell of the next row needs to match or alternate based on the grid geometry, not just the previous cell.
Ensure your loops match the exact variable names provided in the CodeHS starter code template (e.g., i and j vs r and c ).
: Since CodeHS assignments vary slightly by version (Karel vs. Python), make sure your function names ( ) match your specific course requirements. Java Karel
Let’s break down exactly how the code works: