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## 8 Queens Puzzle

Published on Sunday, January 08, 2012 in , , , , ,

Martin Gardner once said that no other geometrical pattern has been so thoroughly exploited for recreational purposes as the checkerboard.

That's especially true at Grey Matters, where you can find puzzles like the Knight's Tour, Knight Shift, and others. Today, however, we focus on the queens!

This week's episode of Scam School returns to the Stanford Chess Club with another classic chess puzzle, known as the Eight Queens Puzzle. If you're not familiar with how a queen moves and captures in chess, here's a brief article and a short video that will explain.

Once you understand the basics, watch the video below, put pause at the 1:45 mark, just as the chess club members start trying to solve the eight queens puzzle. After the pause, scroll past the video and try the puzzle here at the end of this post!

This online version of the puzzle was written by Patricio Molina, who has generously shared it. I've had to make a few modifications to the original version to get it to work on the blog, so you may want to compare it to the original version here.

To play the online version below, simply click on any empty square to place a queen there. Clicking on any square with a queen in it will remove that queen. If you place a queen so that it is attacking 1 or more queens, the squares of the attacking queens will turn red. Your goal, of course, is to place eight queens on the board so that none of them are attacking any of the other queens. You'll know you've done this when all the squares with queens on them turn green.

When you either succeed or decide to give up, finish watching the video above to find out who solved it first, and Brian Brushwood's simple method for being able to remember the placement.

Interestingly, there are 92 possible ways to solve the puzzle, but if you don't count patterns that are rotations or reflections of each other, there are only 12 unique solutions. If you're interested in memorizing more of these patterns, note that each of the 12 solutions has a queen on a border square that is forth from a corner, and that spacing the queens a knight's move apart is often helpful.

How did you do in solving the puzzle? Let me know in the comments.