Sudorku redorx

Another, somewhat drier, question that occurred to me: what is the total number of possible solution grids for a sudoku puzzle? I.e., how many ways are there to consruct a 9x9 grid that has "the sudoku property"?

Su dork u

So this nonsense is popular now. I really don't get it - one grid filled with numbers is about the same as another, to me. With crossword puzzles, at least, the clues can be crafted with varying degrees of cleverness - not to mention 26 > 9.

However, it irks me that there might be peabrains running around getting good at these goofy puzzles and then having a valid claim of mental superiority when I can barely solve the "medium" puzzles in the Wed./Thurs. WaPo. So I've been practicin' some. It's all kind of tedious, but the most tedious part is checking the answer when I'm done.

So here's the nut: In the absence of an answer key, what is the fastest way to check that a su-dork-u grid contains one and only one of each digit in each row, column, and 3x3 box? Put another way: Call each row, column or box an "element"; what is the minimum number of elements that need to be checked for having each digit exactly once in order to be sure that all 27 elements have that property?

Doctored Photo #7

Identify the source of this edited photo and win ten points.

Doctored Photo #6

Here's a chance for a benchwarmer to get on the scoreboard. Five points.

Doctored Photo #5

This one should be within reach of casual news junkies. Ten points to whoever can identify the source.