sudoku solver in kotlin
======== question ========
[0, 0, 4, 3, 0, 0, 2, 0, 9]
[0, 0, 5, 0, 0, 9, 0, 0, 1]
[0, 7, 0, 0, 6, 0, 0, 4, 3]
[0, 0, 6, 0, 0, 2, 0, 8, 7]
[1, 9, 0, 0, 0, 7, 4, 0, 0]
[0, 5, 0, 0, 8, 3, 0, 0, 0]
[6, 0, 0, 0, 0, 0, 1, 0, 5]
[0, 0, 3, 5, 0, 8, 6, 9, 0]
[0, 4, 2, 9, 1, 0, 3, 0, 0]
========= answer =========
[8, 6, 4, 3, 7, 1, 2, 5, 9]
[3, 2, 5, 8, 4, 9, 7, 6, 1]
[9, 7, 1, 2, 6, 5, 8, 4, 3]
[4, 3, 6, 1, 9, 2, 5, 8, 7]
[1, 9, 8, 6, 5, 7, 4, 3, 2]
[2, 5, 7, 4, 8, 3, 9, 1, 6]
[6, 8, 9, 7, 3, 4, 1, 2, 5]
[7, 1, 3, 5, 2, 8, 6, 9, 4]
[5, 4, 2, 9, 1, 6, 3, 7, 8]
took 890353 ns
...