7 Candles In A Room

Problem:

On a cold Friday evening as you are up reading an old book on your porch overlooking the Pacific, a great winged and tentacled creature rises from the dark waters and seizes you. Its octopus arms drag you down into tremendous depths.

When you awaken you are surprised to be alive, and doubly surprised to find yourself in a small room with a circular table in the center. You get the sense that you are deep underwater, and only some unseen mystical barrier prevents a torrent of water from flooding the room.

On the table are seven lit candles in a circle. You hear a deep voice echoing in your mind. It tells you that you must extinguish all seven candles, and should you fail to do so, you will never see land again. When you blow out one candle in the circle, the two neighboring candles are extinguished as well. If you blow on a candle that has already been extinguished, it will relight. And if there is an extinguished candle next to the one you blow on, it also will relight.

To put it another way: When you blow on a candle, it - as well as the candles on either side - will change from lit to unlit, and vice versa.

How do you extinguish all seven candles? What is the least number of moves you can take to extinguish them all?
 

Hint:

Blowing on the same candle twice is essentially the same as not blowing on it at all. Blowing on the same candle three times is the same as blowing on it once.

At first, it may seem like extinguishing all the candles is impossible and you are doomed to drown in the realm of Cthulhu. But the solution to this riddle is simpler than you might think. 

 

Solution:

How do you extinguish all seven candles? Click here to reveal

There is no reason to blow on the same candle more than once. As the hint points out, blowing on the same candle twice is the same as not blowing on it at all, and three times is the same as once. If you start blowing on each candle one at a time, ignoring the effect on other candles, you will quickly realize that this is the solution: blow on each candle once. You can go in order, from the first candle you blow on around the circle, and by the time you blow on the seventh candle all the candles will be extinguished. You can also blow on the candles in any order you want, so long as you blow on each one once, and by the time you are done all the candles will be extinguished. This is the minimum number of moves you can make to extinguish all the candles: seven.

 

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