## Saturday, October 28, 2017

### Tic-Tac-Toe

In a standard game of Tic-Tac-Toe, players take turns placing X's and O's on a 3x3 grid until one player makes three-in-a-row in any direction (horizontally, vertically, or diagonally). Because of these rules, you can only place a maximum of five of either symbol on the board during a game, often ending in a draw.

Can you place six X's on a Tic-Tac-Toe board without making three-in-a-row in any direction? (Without placing any O's.) Click below for the solution.

Dan said...

Enjoy each of the puzzles you post. This one, my approach was to use the 4 "center" boxes on the 4 outside rows to start. OK, just 2 to go. Then I figured the center was all sorts of bad, so I chose a corner randomly (doesn't matter which). Then it was just a question of finding which of the remaining 3 boxes didn't blow the thing up.

Good challenge for a Saturday morning. BTW, I assume you're familiar w/ Martin Gardner's books (you probably have all of them I'd guess). Some of his puzzles are simple and elegant, but some of them go a bit over my head.

Cheers!

Bill the Lizard said...

Dan,

Thanks, I'm glad you liked the puzzle.

I came to the solution in much the same way, only after considerable trial and error. (Starting in the center or a corner is a slow way to go about this.) At one point I did end up with X's in the four side squares, and the solution came to me pretty quickly from there.

I do have several of Martin Gardener's books, but I'm sure not all of them, since he wrote so many. Sam Loyd and Raymond Smullyan are two of my other favorites if you like Gardener's books.