You don’t have to be a chess player, or even know the rules of chess, to have a good time with today’s puzzle. All you need to know is that the queen is the most powerful chess piece – she can move as far as she likes in any direction: forward and back, sideways to the right or left, and diagonally. The diagram on the right illustrates the queen’s awesome power.

Today’s challenge is to place eight queens on a chess board such all 64 squares are attacked and no two queens are attacking each other. To make this puzzle easy and fun, I’ve created a custom software simulation, which you can use to try to solve it yourself right here on my blog (so you don’t even need a chess set). Just click on a square below to add a queen, and keep going until you’ve placed eight queens or run out of space with fewer than eight. You can click on an existing queen to undo a placement and there’s a reset button below the board in case you want to start over. You can also click the “solve” button to have your computer quickly find a random solution (there are many). Have fun and leave me a comment if you manage to solve this one!

Queens placed: 0

Covered (occupied + attacked) squares: 0

5 thoughts on “Saturday Puzzle #26 – The Eight Queens Problem”

Got it! Not sure if I really figured anything out, just saw some likelihoods and kept trying until it worked. Thanks for the new game!

Very good Marc. I’ve two solutions for this problem.. Shame my iPad or the webapp doesn’t have a screenshot feature.

Interesting it turns out you can do screen grabs on an iPad, press the home and off button together. Fancy that ;-)

Got it–but it was only partly by design.

A reverse challenge might be, how few queens can you use to attack all the unoccupied squares? I got it down to five.

Got it! Not sure if I really figured anything out, just saw some likelihoods and kept trying until it worked. Thanks for the new game!

Very good Marc. I’ve two solutions for this problem.. Shame my iPad or the webapp doesn’t have a screenshot feature.

Interesting it turns out you can do screen grabs on an iPad, press the home and off button together. Fancy that ;-)

Got it–but it was only partly by design.

A reverse challenge might be, how few queens can you use to attack all the unoccupied squares? I got it down to five.