## Sudoku Troubleshooter #1 – Row/Column/Block

Occasionally, I get mail from fans of the site who need help with a puzzle. I’ve decided to devote the next few blog entries to puzzle solving techniques. If you want help with a particular Krazydad puzzle (especially puzzles that are easier than “Super Tough”), drop me a note, and I’ll troubleshoot your problem too!

Our first puzzle is from Margaret, who got stuck solving the daily Challenging puzzle from May 12th. If you’d like to try your hand at this puzzle, you’ll find the original here.

Here’s the puzzle at the point Margaret got stuck.

Looking at just the 1s, these appear to be possible squares for ones:

I’m gonna use the *row/block* and *column/block* technique to narrow them down further. Looking at the block on the lower left, I can see that the 1 in that block must occur in the first column.

That means we can eliminate 1 from all the other squares in that column.

Now, looking at the center block, I can see that 1 must occur in that block in row 4. So I an eliminate 1 from other squares on row 4.

Now we’ve found a 1!.

You can use the same type of logic to find a 2. Try it!

August 23rd, 2011 at 9:37 pm

I call these “guns”. In this case, a couple of instances of a “one gun”.