Its ok now. Thanks for quick fix!

I've found next tests in random tests suite:

Incorrect answer for board:

000|000|080
258|790|000
041|036|257
---+---+---
106|179|504
109|400|076
004|368|910
---+---+---
792|600|143
000|010|005
005|203|008

Fourth and Fifth lines are started from 1 "106......" and "109......". Thats invalid sudoku board, because we have duplicate value (1) in first column.

Incorrect answer for board:

009|088|040
002|000|630
304|625|870
---+---+---
405|168|090
080|509|120
100|702|500
---+---+---
008|203|400
006|890|307

In first line we have duplicate value (8) (...088...)

And so on.

In Java version I've found next fixed test with unbalanced parenthesis (26 left, 27 right):
(((()()(()(()()()(()()(()()(()))))))(()))()(()()()))) (note 4 closing brackets at the end).

Following error message for this test is:
2*(2*(2*(1+1+2*(1+2*(1+1+1+2*(1+1+2*(1+1+2*(1))))))+2*(1))+1+2*(1+1+1))) = 790 ... (note 3 closing brackets at the end).

It should be fixed.

Thank you for the answer!

I understand how it gets the index in string, where is really a second 'c', but how it returns -1 in other cases?

You are absolutely right, it was not working properly for cases where the arrow starts from the beginning of the string. My python solution contained the right version of the operator, but somehow I mistranslated it. Sadly there were no fix tests with an arrow starting at the beginning of the string, so thank you very much for your insight!

I updated the solution, and also added a sample test with string "-->" to cover this case.

In searchArrows method (7th line): while (j > 0 && string.charAt(j) == ...) {

Should be: while (j >= 0 && string.charAt(j) == ...) {

Mine solution pass by luck (after almost 10 attempts), but others cannot solve this kata in Java for this reason (IMO).
In any case, I appreciate your contribution for Java branch. Thanks for all your work!

Lambda Calculus translation

When I saw low satisfaction rating and few completions for this kata I was afraid. If you in doubt will or not just jump in this kata. It is solveable, well designed and can give you good experience. Many thanks for Gigabyte series!

Maybe I'm late with help.
You are completing hand with fifth 3 in this case.
Description says: Note that there are EXACTLY 4 identical copies of each kind of tiles in a deck.

Thanks! :)

Many thanks for kingdoms episodes!

For this task your solution is good enough. I'll vote it up.

Many thanks for feedback. I'm not a programmer, and I do not pretend on Best Practice Solution for all tasks that I've solved on this webcite. In my opinion this task is not about performance. My O(n^2) solution was good for test conditions and I'm happy. I've recommend 6kyu kata Grazing Donkey by hobovsky and 6kyu kata Count a Spiral by Flurin Brühwiler. This katas is about performance. Good luck and have fun.

p/s Your solution on this kata in top 10% in my opinion and I'll vote it up.