This report includes the Problem Statement, Algorithm Analysis, the Corrected Code Solution, and a detailed Code Breakdown to ensure the "fixed" requirements are met (specifically addressing the common issue where the code runs infinitely or crashes due to missing decrement logic).
"red") and Black ("black")import turtledef draw_square(color): turtle.color(color) turtle.begin_fill() for _ in range(4): turtle.forward(50) turtle.left(90) turtle.end_fill() turtle.forward(50)
def next_row(): turtle.penup() turtle.backward(400) turtle.right(90) turtle.forward(50) turtle.left(90) turtle.pendown()
def main(): turtle.speed(0) for row in range(8): for col in range(8): if (row + col) % 2 == 0: draw_square("red") else: draw_square("black") next_row() turtle.hideturtle() turtle.done()
main()
If you paste your specific broken code or the exact error message from CodeHS, I can give you the exact line-by-line fix. Would you like that?
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
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. 916 checkerboard v1 codehs fixed
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. This report includes the Problem Statement , Algorithm
For the CodeHS exercise 9.1.6: Checkerboard, v1, the goal is to initialize a
list (grid) and then use nested loops to set specific elements to
to create a checkerboard pattern in the top and bottom three rows, while leaving the middle two rows as Final Correct Code
# Create an 8x8 board filled with 0s board = [[0] * 8 for _ in range(8)] # Use nested for loops to modify specific rows for row in range(8): for col in range(8): # Top 3 rows (0, 1, 2) and bottom 3 rows (5, 6, 7) if row < 3 or row > 4: # Checkerboard condition: sum of indices is even if (row + col) % 2 == 0: board[row][col] = 1 # Print the board using the provided function print_board(board) Use code with caution. Copied to clipboard Step-by-Step Explanation Initialize the GridCreate an list of lists where every element starts as
. You can do this quickly using a list comprehension: board = [[0] * 8 for _ in range(8)].
Identify Target RowsThe instructions require modifications only to the top 3 rows (indices ) and the bottom 3 rows (indices ). The middle two rows (indices ) must remain all
Apply Checkerboard LogicInside a nested loop, use the mathematical property of a checkerboard: an element should be if the sum of its row and column indices is an even number. Example: At board[0][0], (even), so it becomes Example: At board[0][1], (odd), so it remains
Verify with print_boardPass your modified board variable into the print_board() function already provided in the CodeHS editor to see the visual output and pass the test cases. Common Troubleshooting Tips
"You should set some elements to 1": This error usually means your if condition for the rows is wrong or you aren't actually assigning board[row][col] = 1.
Middle Rows: Ensure your row check is if row < 3 or row > 4:. If you use row <= 3, you will incorrectly modify the 4th row.
Solved 9.1.6: Checkerboard, v1 Save 1 # Pass this function a Expected Behavior
For the CodeHS 9.1.6: Checkerboard, v1 exercise, the goal is to create an 8x8 grid (a list of lists) where specific rows are populated with 1s to represent checkers and others with 0s to represent empty spaces. The Problem Brief You are required to: Initialize an 8x8 grid filled with 0s. Use a nested for loop to modify the grid.
Set the top 3 rows (indices 0, 1, 2) and the bottom 3 rows (indices 5, 6, 7) to 1s. Keep the middle 2 rows (indices 3, 4) as 0s. Fixed Python Solution
This approach uses a nested loop as required by the CodeHS autograder.
# 1. Initialize the 8x8 grid with all 0s grid = [] for i in range(8): grid.append([0] * 8) # 2. Use a nested loop to set specific rows to 1 for i in range(8): # Only modify the top 3 (i < 3) or bottom 3 (i > 4) rows if i < 3 or i > 4: for j in range(8): grid[i][j] = 1 # 3. Print the board using the provided function # (Make sure print_board is defined or provided by CodeHS) print_board(grid) Use code with caution. Copied to clipboard Proper Write-Up / Logic
Initialization: We start by creating a list called grid. By looping 8 times and appending a list of eight 0s each time, we build a 2D structure (8x8).
Row Filtering: The outer loop iterates through each row index (i). The if i < 3 or i > 4 condition identifies the rows where checkers should be placed (the first three and last three).
Nested Assignment: The inner loop (for j in range(8)) goes through every column in those specific rows and changes the value from 0 to 1.
Verification: The middle rows (indices 3 and 4) are skipped by the if statement, ensuring they remain empty as requested. Common Pitfall
Many students try to use (i + j) % 2 to create a "true" alternating checkerboard pattern. While that is how real checkers look, Checkerboard v1 specifically asks for solid blocks of 1s at the top and bottom with a gap in the middle.
Solved 9.1.6: Checkerboard, v1 Save 1 # Pass this function a
Running this code will produce a standard 8x8 checkerboard pattern with alternating black and white squares.
Step-by-Step Solution:
rect function.