Hi, for the 'flip' problem, my code works for all my test cases, but I get a run-error when submitting.

I have also fuzzed it with a large number of random test cases for all row lengths, and column lengths, and the program still succeeds with no exception.

Is there any chance we can have access to additional test cases to debug our algorithms? Because I' not sure what to do after fuzzing the possible inputs so thoroughly.

Here is the fuzzing script I'm using to test for runtime errors:

import subprocess
import os
import random
import time

filename = "flip.py"

fuzz_runs = 1000

path = os.getcwd()
file_path = os.path.join(path, filename)

while fuzz_runs > 0:
    rows = 1 + int(999 * random.random())
    cols = 1 + int(999 * random.random())

    values = [["." if random.random() < 0.5 else "x" for c in range(cols)] for r in range(rows)]
    grid_lines = "\n".join("".join(values[r]) for r in range(rows))
    question = f"{rows} {cols}\n{grid_lines}"
    with open("test/22.in", 'w') as f:
        f.write(question)

    result = subprocess.run(['python3', file_path], input=question, capture_output=True, text=True, check=False)

    if result.stderr:
        print(result.stderr)
    else:
        print(result.stdout)

    fuzz_runs -= 1

Run errors (as opposed to wrong answers) on DOM judge are often due to hitting memory limits (1GB limit iirc), whereas on your own machine you might be able to allocate more than that. Might be worth seeing if your code creates a lot of memory for use at any point.

The previous student is correct. As has been mentioned before in various places, Python normally gives a Run-Error when hitting the memory limit.

No, no students will be provided with additional test cases. Exploring test cases and finding bugs yourself is an intended part of the project.

I will also remind you that some of these problems (like FLIP, which is worth 50 points) are meant to be hard. It is not expected that all students will solve them. If you are unable to solve it, move on to a different problem. If it gets to the end of the project and you have not solved all problems, that is how you get a mark less than 100%. It is not expected that all (or many) students will get 100%.

Cheers, Gozz