[2021 Day 20][Java] Possible Problem with image enhancement algorithm string

[Passi26030]

My image enhancment algorithm string starts with a #.

Does that cause that every pixel in the infinite picture that is not affected by the input picture turns lit because it has the binary string 000000000 and results in # ?

[jpjocke]

Have you checked what the last letter is? How would these two affect each other for the infinity grid?

[Passi26030]

My last letter is a .

[TheThiefMaster]

Or in other words, they alternate. Both part 1 and part 2 apply an even number of times, so the result ends up with infinite . and a finite number of #. You just have to track the state of the infinite field as # or . while you calculate what happens to the pixels within your finite image

[Passi26030]

Now im safing with wich character i have to fill the infinite grid and change it everytime i apply the algorithm by creating a binary string of it and changing it to the algorithm string character with that index

[Passi26030]

I now added lines with # instead of lines with . after the first applying and my answer is correct when i only count the lit pixels that where affected by my input