It is possible to use a recursion strategy without using any sudoku-specific solver techniques, and without having to worry about time constraints.

this is illegal, LOL.

LOL

Hi,

It's a numeral system with a base equal to 27.

Decimal is the system you use everyday to count; it's a numeral system with a base equal to 10, it has 10 different digits: 0 to 9.

hexadecimal is another system, with a base equal to 16. It has 16 different digits: 0 to 9, plus A to F. We use it a lot to represent the value of a byte.

0 to 9 in hexadecimal is equal to 0 to 9 in decimal. Then, A is equal to 10, B is equal to 11, C is equal to 12, D is equal to 13, E is equal to 14, and F is equal to 15.

So:

0 in hexadecimal is equal to 0 in decimal

1 in hexadecimal is equal to 1 in decimal

But, 10 in hexadecimal is NOT equal to 10 in decimal

10 in hexadecimal is equal to 16 in decimal

For exactly the same reason, "A " in our base 27 numeral system is equal to 27 in decimal.

If this is still confusing for you, I suggest you read more about numeral systems by following the Wikipedia links I provided.

Cheers

if you're exceeding the call stack size with these test cases, your algorithm is inefficient or incorrect

it's obvious that any recursion answer would be rejected for silly test limits any way that's make no sense :(