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Arctic's Riddle Challenge! - 5 Cards, A magic trick, and the mysterious guesser.


Ăɍȼẗîȼ

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Rules-> Read before you post:

1) Don't post anything that is unnecessary, or stupid.

2) Do not assume anything that shouldn't be assumed. I.e. Can the wizard's escape during the night? They could, but we don't know that.

 

3) You are only allowed to use premises on the question.

4) Solve this problem TOGETHER, as a whole of YCM.

5) If anyone wants to donate, then they are welcome to, any donations would go into prizes other than possible reps.

 


 

Say me and my friend are going to play a magic trick on someone called Bob. (There is some system arranged before hand between me and my friend.)

 

Okay my friend leaves the room.

 

BOB chooses 5 cards. (assuming a STANDARD 52 card deck.)

 

I CHOOSE a card to hide from the 5 cards, and I CHOOSE the order of the remaining cards to place on the table.

 

My friend comes in, and he looks at the 5 cards on the table, and he is able to tell exactly the card that I hid. (note he hasn't seen the 5 original cards)

 

Bob is absolutely stunned.

 

What was the system arranged before hand?

 

Assume the worst case when Bob chooses cards.

 


[spoiler=Past Problem #1]

Say there are 101 wizards, sentenced to the Death by the King Wizard.

 

The King Wizards says to the wizards:

 

"I am a good King. Tomorrow, I will line you all up in a single file straight line, and remove your wands so you can't use magic. I will place a hat on each wizard, it is either Pink, or Cyan. You must guess the color of your hat! If you get it right, then you live, if you should get it wrong, you'll BURN!!!"

 

"Of course, to be fair, the wizard at the end of the line gets to see all of the hats in front of him..., but in exchange for that, he must go first! You will have tonight, to say your last words... (You are not allowed to say anything but guess the color of your hat.)"

 

Of course, none of the wizards wanted to die. So they talked, and brainstormed all night long. They came up with a plan.

 

What plan will save the most wizards in the worst case?

 

For example:

First wizard says the second wizard's hat color instead of guessing their own. The second wizard says whatever the 1st wizard says. In the worst case, this saves 50 wizards.

 

Congrats to Deja Cru!

 

 

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I know this. Well sorta.

 

I heard it this way: There is a town that has no mirrors and a king. He orders all the people in the village with blue eyes to leave. Now they can't see there own eye color and they can't talk about it. Somebody has blue eyes and everybody sees each other everyday. How do you know if you have blue eyes.

 

If only 1 person has blue eyes, they will see that nobody else has blue eyes and they won't leave. If two people have blue eyes, they will see someone else with blue eyes and stay the first day. The next day they will see that the person with blue eyes stayed and will know that that person saw someone with blue eyes. Since the only person in the village who could have blue eyes besides the other person is you, you leave. For every person with blue eyes it takes 1 day.

 

Not sure how to apply this to your theory, but it does work.

 

I actually think I heard this case, but I can't remember the answer.

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