: The inner loop ( for j in range(8) ) goes through every column in those specific rows and changes the value from 0 to 1 .
CodeHS 9.1.6 Checkerboard v1: FIXED & WORKING! Struggling with the logic for the Checkerboard problem in Python? I finally got the
This code initializes an 8x8 grid of zeros and then fills the top three and bottom three rows with a checkerboard pattern of 1s.
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.
If you are working through the JavaScript or Karel variant of 9.1.6, the logic remains identical even if the syntax shifts. Instead of coordinates, Karel needs to know if it is facing east on an even street or an odd street. If your environment uses Karel the Robot: Put a ball down if frontIsClear() . Move two steps instead of one to naturally skip spaces. 916 checkerboard v1 codehs fixed
Now that you've mastered the basic grid, are you ready to tackle Checkerboard v2 and add more complex patterns?
You are tasked with creating a checkerboard pattern using a grid of squares. The board should have and 8 columns of alternating black and red squares. The top-left square should be red.
The core challenge of the "916 Checkerboard" is not drawing the squares, but determining their color. This is where many early attempts fail. A common misconception is that the color alternates simply based on the loop counter (e.g., if i is even, red; if i is odd, black ). While this works for a single line, it fails on a grid because the first square of a new row must be the opposite color of the last square of the previous row.
# Reset X for new row x = -200
11111111 11111111 11111111 00000000 00000000 11111111 11111111 11111111
However, getting the "fixed" version—where the grid perfectly alternates colors without overlapping or skipping—can be tricky. The objective is to create an
The pattern doesn't match the required alternating structure.
The easiest way to decide if a cell should be a 0 or a 1 is to add its row index and column index together: : The inner loop ( for j in
: Ensure your row check is if row < 3 or row > 4: . If you use row <= 3 , you will incorrectly modify the 4th row.
For a standard 8x8 checkerboard, you create an outer list named board with 8 rows. Each row is itself a list containing 8 values (either 1 or 0 ). The nested nature of 2D lists means you can access any individual cell using two indices: board[row][column] . Understanding this concept is essential for manipulating the grid.
The objective of 9.1.6 Checkerboard V1 is to populate a two-dimensional array of integers or booleans so that no two adjacent cells horizontally or vertically share the same value. In a standard representation: represents a black square (or one state). 1 represents a white square (or the opposite state). The Desired Matrix Output
At first glance, a checkerboard appears trivial. It is simply a grid of alternating red and black squares. A student’s first instinct is often to "hard code" the solution: draw a red square, then a black square, then a red square, and manually position them one by one. However, the "916" specification usually implies a large grid (likely 8x8 or similar dimensions), making hard-coding impractical and tedious. The "fixed" solution abandons the manual approach in favor of automation, using nested loops to traverse the rows and columns. I finally got the This code initializes an
Make sure the pattern alternates correctly ( Conclusion
Are you having trouble with the version of this assignment, or is the autograder still giving you a specific error message?