• If you raise on an invalid grid, that is just a passing test, it won't stop the tests.
• flushing: print("balbla", flush=True)
• the behavior you describe most likely points to an infinite while loop. To spot it, you can print stuff to the console from each of your loops, to wee which one is going crazy.

Not a kata issue => closing.

The shortest solutions I can see in JS is about 8 lines, however most are quite larger. For example mine is 35. There are certainly mathematical elements to this kata however its far more than simply plugging in a formula.

If you use Python, you can print and flush it to see some value even if the code halts with a timeout. print(some_value, flush = True)

12000ms limit is the total time limit.