Bobby Braingle has a bit of a dilemma on his hands. He has accidentally locked his puzzle collection in a combination safe. Being rather dim and absent-minded, he has gone and forgotten the combination.
This safe uses letters instead of numbers. The six letters used in the combination are Z, Y, X, W, V, F. No letter is repeated. Here are three incorrect guesses
Bobby has already made: X Y Z W F V Z V W X Y F V W F Z X Y In the first guess, only one letter is in its correct place In the second guess, only two letters are in their correct places. In the third guess, only three letters are in their correct places. Each of the six letters is in its correct place once.
What is the correct combination needed to rescue the puzzle collection?
The combination was either VYWZXF or ZVFWXY. He only needs to try these two in order to rescue his puzzle collection. Solving this puzzle requires a method of trial and error. Start with the first combination and assume that one of the letters is in the correct position. Assuming the Y is correct, we know that the V in guess 2 is in the wrong position so it must be in the correct position in guess 3. Likewise W in guess 3 is wrong, so its position in guess 2 must be correct. If a W's position in guess 2 is correct, then F in guess 3 must be incorrect, which means its position in guess 2 is correct. Continue this logic until you arrive at the answer. (If your first assumption was incorrect, you would arrive at an impossible situation and have to start over.
It's like that game Mastermind, where someone makes a sequence with four colored balls and you have to guess what it is. I got lucky and found the first correct answer pretty quickly, but I didn't think to check if there was a second solution.