645 Checkerboard Karel Answer Verified Jun 2026

turnRight(); move(); turnRight();

fillRow() (frontIsClear()) move();

: Always check frontIsClear() before every move() to prevent Karel from crashing into walls. Verified Solution Pattern (JavaScript) Stanford's - Karel The Robot & Checkerboard Problem 645 checkerboard karel answer verified

for (var i = 0; i < size; i++) for (var j = 0; j < size; j++) // Draw a square if (currentColor == black) putDown(); move(size); turnLeft(); move(size); turnRight(); putUp(); currentColor = white; else putDown(); move(size); turnLeft(); move(size); turnRight(); putUp(); currentColor = black;

if (frontIsClear()) move();

// Assuming 8x8 checkerboard, starting from (1,1)

The while(leftIsClear()) loop in the start function keeps Karel moving upward. The conditional if (rightIsClear()) check ensures that if Karel reaches the top-right corner of an odd-dimensioned world, the program terminates gracefully instead of throwing a wall-collision error. If your world is only one column wide,

If your world is only one column wide, your code might crash if you don't check leftIsClear() before trying to turn.

function start() putBeeper(); // Start the pattern fillRow(); while (leftIsClear()) transitionToNextRow(); fillRow(); function fillRow() while (frontIsClear()) move(); if (frontIsClear()) move(); putBeeper(); function transitionToNextRow() // This logic changes based on Karel's current orientation // to ensure the alternating pattern persists upward. if (facingEast()) turnLeft(); checkAndMoveUp(); turnLeft(); else turnRight(); checkAndMoveUp(); turnRight(); Use code with caution. // Start the pattern fillRow()