You're welcome!

thanks man

How does this work?

Because those intervals aren't overlapping, there is a gap between 5 and 6.

then in the smample test case why is
[1,5],[6,10] not treated as 1 to 10 ?

the result provided is 8.

If the first layer of recursion returns None, then the puzzle isn't being returned. So if the function takes in the original matrix, and in the loop if puzzle[y][x] == 0: condition is satisfied, then it will return nothing.

@Blind4Basics please

right. But doesn't that just recursively return none? and then my final return returns the puzzle? what PUZZLES me (groans) is that I can print the finished puzzle but cannot return it.

11th line in your solution. You're returning None.

please lol I can literally print the solution but I cannot return it. I wanna rank up so bad.

could you please take a look at my code? I'll mark it as spoiler. I'd really appreciate it.