9.1.7 Checkerboard V2 Answers Fixed (2026)

Mastering CodeHS: The Complete Guide to 9.1.7 Checkerboard v2 Answers

If you've landed on this article, you're likely working through the CodeHS Java course (specifically the "Methods and Control Structures" or "Basic Java" units) and have hit the infamous 9.1.7 Checkerboard v2 exercise. Don't worry—you're not alone. This problem is a rite of passage for learning nested loops, modulus logic, and graphical user interface (GUI) manipulation in Java.

This article provides a full breakdown of the problem, the logic behind the solution, the correct code answer, common mistakes, and how to truly understand the concepts so you can pass the autograder on the first try.

Frequently Asked Questions (FAQ)

Q: Can I use a different number of rows and columns?
A: Yes, but the 9.1.7 autograder specifically expects 8x8. Changing it will fail the test.

Q: Why does my board start in the wrong corner?
A: Check your x and y calculations. x = col * size ensures the first column starts at 0. If you accidentally add an offset, correct it.

Q: How do I submit without getting a "missing main method" error?
A: The GraphicsProgram class has its own main method internally. You do not need to write public static void main. Just extend GraphicsProgram.

Q: I see a gray square instead of a red one. Is my code wrong?
A: No. Some versions of 9.1.7 use black and gray. If the sample image shows gray, replace Color.RED with Color.GRAY.

Q: The autograder says "Expected output: 8 rows of alternating squares" but I have it.
A: Ensure your canvas size is exactly 400x400 (since 8 * 50px = 400px). If you used getWidth(), the board might be off by a few pixels if the window isn't perfectly square.

7. Sample Code (Python + graphics.py — common for v2)

from graphics import *
def draw_checkerboard(win, rows, cols, size, color1, color2, start_color1):
for r in range(rows):
for c in range(cols):
x1 = c * size
y1 = r * size
x2 = x1 + size
y2 = y1 + size
rect = Rectangle(Point(x1, y1), Point(x2, y2))
if (r + c) % 2 == 0:
rect.setFill(color1 if start_color1 else color2)
else:
rect.setFill(color2 if start_color1 else color1)
rect.draw(win)
Final verification checklist

All per-row/per-column/region counts met.
No forbidden adjacencies present.
Global parity/tiling constraints respected.
Any extra conditions (connectivity, alternation) satisfied.

If you share the exact rule text or an image of your “9.1.7 Checkerboard v2” puzzle, I’ll produce a precise, cell-by-cell solution and final grid layout.
The solution to the CodeHS Python 9.1.7: Checkerboard, v2 assignment involves using a function to generate a 2D list (a list of lists) where alternating elements represent a checkerboard pattern. Correct Answer Code
def board(): my_grid = [] for i in range(8): # Even rows start with 0 if i % 2 == 0: my_grid.append([0, 1] * 4) # Odd rows start with 1 else: my_grid.append([1, 0] * 4) # Print each row in the grid for row in my_grid: print(row) board()  Use code with caution. Copied to clipboard 1. Initialize the grid container
The first step is to create an empty list, often called my_grid, which will hold the rows of your checkerboard. Since a checkerboard is typically
, you will use a loop that runs 8 times to create 8 distinct rows. 2. Differentiate even and odd rows
A checkerboard pattern relies on alternating starting values. You use the modulo operator (i % 2 == 0) to check if the current row index is even or odd. Even rows: Start with 0 (e.g., 0, 1, 0, 1...). Odd rows: Start with 1 (e.g., 1, 0, 1, 0...). 3. Use list multiplication for efficiency
Instead of writing a nested loop to fill each individual cell, you can multiply a small list to fill the row. Multiplying [0, 1] by 4 creates a list of 8 elements: [0, 1, 0, 1, 0, 1, 0, 1]. This is a concise way to ensure each row has exactly 8 columns. 4. Print the final 2D structure
After the grid is populated with all 8 rows, you must iterate through my_grid and print each inner list. This displays the board in a readable format rather than printing the entire nested list on a single line. Final Result The final code uses a single function to build an 9.1.7 checkerboard v2 answers
grid of alternating 0s and 1s by checking row indices and appending pre-formatted lists, resulting in a perfectly formatted checkerboard pattern.
Do you need help with nested loops for a more manual version of this grid, or
9.1.7 Checkerboard, v2 I got this wrong, and I can't ... - Brainly
Since I don’t have access to proprietary problem statements or answer keys, I’ll provide a deep, analytical piece on what such a problem typically involves, the patterns behind it, and how to think through a solution — so you can derive the answer yourself, or understand it at a deeper level.

Conclusion
The 9.1.7 Checkerboard v2 assignment is a rite of passage for Java students. The key to success is understanding the relationship between row/column indices and color parity. Remember the golden rule: (row + col) % 2 == 0 for one color, odd for the other.
By using the code and explanations provided in this article, you should now have both the direct 9.1.7 checkerboard v2 answers and the conceptual knowledge to explain your solution. Happy coding, and may your checkerboard always alternate perfectly!

Disclaimer: This guide is intended for educational purposes. Always check your school’s academic integrity policy before using online resources. The best way to learn is to type out the code yourself and experiment with modifications.
The fluorescent lights of the computer lab hummed, a soundtrack to the mounting panic of a dozen Intro to Java students. It was Friday, 3:45 PM. The deadline for the "Nested Loops" unit was looming like a storm cloud.
Leo stared at his screen, his eyes blurring. The objective seemed simple enough: 9.1.7 Checkerboard v2. Draw a grid. Black square, white square, black square. But the code on his screen was producing a pattern that looked less like a chessboard and more like a barcode gone wrong.
He ran the code again.
Row 1: Black, White, Black, White. (Perfect.)
Row 2: Black, White, Black, White. (Disaster.)
"It’s offset," Leo muttered, burying his face in his hands. "It’s supposed to be offset."
"You look like you're trying to calculate the trajectory of a Mars rover, but you’re just staring at a black screen."
Leo looked up. It was Maya, the TA. She was holding a mug of tea and looking amused. She pulled up a chair next to him.
"It’s 9.1.7," Leo groaned. "The Checkerboard. I can get the rows to alternate colors, but I can’t get the columns to sync up. My rows are identical. It’s just stripes."
Maya nodded. "Ah, the classic v2 trap. Did you look at the 'answers' in the documentation?" Mastering CodeHS: The Complete Guide to 9
"I tried," Leo admitted. "I searched '9.1.7 checkerboard v2 answers' online, but I just found a bunch of code blocks with no explanation. If I copy-paste it, I get the points, but I won’t know why it works. And the test is next week."
"Good instinct," Maya said. "Copying the answer key is like eating the menu instead of the meal. Let’s figure it out the hard way."
She pointed to his loop structure on the screen. "Show me your logic."
Leo pointed to the for loop for the rows. "I have i for the rows and j for the columns. If j is even, I draw black. If j is odd, I draw white."
"Right," Maya said. "So, for every row, column 0 is black, column 1 is white. That works for Row 0. But what happens when you jump down to Row 1?"
Leo paused. "Well... the loop restarts. So j starts at 0 again. Column 0 is black again."
"Exactly," Maya said. "So Row 0 and Row 1 look identical. You're forgetting to factor in where you are vertically. You're only looking at the horizontal position."
"So... it’s a math problem?"
"It’s a coordinate problem," Maya corrected gently. "Think of a coordinate plane. You have an X and a Y. The color of a square depends on the sum of its coordinates."
She grabbed a piece of scratch paper and drew a grid. She labeled the top left corner (0,0).
"At (0,0), the sum is 0. Even. So, Black," she said.
"At (0,1), the sum is 1. Odd. So, White."
"Now, look at the start of the next row. (1,0). The sum is 1. Odd."
Leo’s eyes widened. "So if the sum is odd, it inverts the starting color automatically."
"Right," Maya smiled. "You don't need a complex if-else chain to check the row number separately. You just need to check if (row + column) % 2 == 0."
Leo turned back to his keyboard. He highlighted his clumsy logic:
if (j % 2 == 0)
He deleted it and typed the new condition:
if ((i + j) % 2 == 0) Frequently Asked Questions (FAQ) Q: Can I use
He held his breath and hit Run.
The Java console sprang to life. The canvas rendered.
Row 0: Black, White, Black, White.
Row 1: White, Black, White, Black.
Row 2: Black, White...
A perfect checkerboard.
"Yes!" Leo whispered, pumping a fist.
"That," Maya said, standing up, "is the difference between finding the answers and finding the solution. You didn't just pass 9.1.7; you understand how to map a grid."
"Thanks, Maya," Leo said, watching the green "Check Passed" box appear on his screen.
"And hey," she called over her shoulder as she walked away. "Next time, don't look for the answer key. Look at the coordinates. Usually, the logic is simpler than the panic allows you to see."
Leo smiled, saved his file, and closed the lab. The checkerboard was solved, and for the first time all afternoon, the hum of the lights sounded almost like a victory song.
The solution to the 9.1.7: Checkerboard, v2 exercise on CodeHS involves creating a function that generates an grid of alternating Correct Code Implementation
The following Python code defines the checkerboard function and uses nested loops to build the grid. Use code with caution. Copied to clipboard Step-by-Step Logic
Iterate Through Rows and ColumnsUse a nested for loop where the outer loop represents the row index and the inner loop represents the column index , both ranging from
Determine Alternating ValuesA checkerboard pattern is defined by the sum of its coordinates. If is even, the cell gets one value (e.g., ); if it is odd, it gets the other (e.g.,
). Alternatively, you can check if the row index is even to decide if the row starts with
Format the OutputWithin the outer loop, convert the list of integers into a string using " ".join() to ensure the numbers are separated by spaces as required by the exercise. ✅ Final Output The resulting pattern should look like this:
0 1 0 1 0 1 0 1 1 0 1 0 1 0 1 0 0 1 0 1 0 1 0 1 1 0 1 0 1 0 1 0 0 1 0 1 0 1 0 1 1 0 1 0 1 0 1 0 0 1 0 1 0 1 0 1 1 0 1 0 1 0 1 0  Use code with caution. Copied to clipboard
Do you need help with the 9.1.6: Checkerboard, v1 version or a different CodeHS module?
9.1.7 Checkerboard, v2 I got this wrong, and I can't ... - Brainly
Deep Dive: Understanding "9.1.7 Checkerboard v2"