We cant help without seeing your code ~~ and in what langugae? ~~~~~

Why don't you simply convert the input to a string (if it is already a string, that'll be ok too)? It's not a kata issue, use Question instead when the problem is with your code.

If method gets number, it should return string.

It's already there, isn't it?

Yes, that's how sudoku board validation works, and I think it's explained in description too. If any of these rules is broken, then it's not complete.

Because there may be numbers repeating in horizontal or vertical lines.

If you're only solving for 3x3 squares, you might miss some boards that are invalid.

3751 Python completions

2946 JavaScript completions

Yeah, sure.

You didn't say the language, but if it is Python the tests are fine.

Most likely your not going through the full array and are missing the being of the array or the end of it.

Tests in javascript work fine, it's likely your code that we can't see what's wrong. Try posting it and marking your post as having spoiler content.

Same issue - Expected: 0, instead got: 1111111; When i put only 1's in the array, code return 0. Cannot understand where is the mystake?

The problem is, the last test case is so big logging the input is not possible.

I think you need to post your code (with spoilers) here.

As @Chrono79 said, this is a question not an issue.

... and each of the nine 3x3 sub-grids (also known as blocks) contain all of the digits from 1 to 9.

You're failing that.

This is a question, not a kata issue (please change the label if you still can). 2552 JavaScript (is that the language you're talking about?) Completions means a lot of people could complete it without problem. Try using console.log(arr) to see what the input is.