Hello, World

#1

Post by sethbannon » Mon, May 18, 2015, 12:06 AM UTC

Hello, World
m.whitehouse.gov

Re: Hello, World

#2

Post by alexashka » Mon, May 18, 2015, 2:07 AM UTC

If the answer is 'at least one of them always write down "heads or tails"', then lol

Re: Hello, World

#3

Post by SMackinnon » Mon, May 18, 2015, 2:13 AM UTC

Spoiler:

Bob always chooses the same as his flip, Alice always chooses the opposite of her flip.

  B A
  H H - Bob chooses heads, Win
  H T - Alice chooses heads, Win
  T H - Alice chooses tails, Win
  T T - Bob chooses tails, Win

Re: Hello, World

#4

Post by sdab » Mon, May 18, 2015, 2:17 AM UTC

SMackinnon wrote: post #3

Spoiler: Bob always chooses the same as his flip, Alice always chooses the opposite of her flip. B A H H - Bob chooses heads, Win H T - Alice chooses heads, Win T H - Alice chooses tails, Win T T - Bob chooses tails, Win

Yep, its a nice problem. Reformulating it such that there are two possibilites (the coins are either different or the same) rather than four (permutations of two coins) is the way to solve the problem.

I was going to post a hint rather than the solution, but you beat me to the punch.

Re: Hello, World

#5

Post by furyofantares » Mon, May 18, 2015, 2:19 AM UTC

SMackinnon wrote: post #3

Spoiler: Bob always chooses the same as his flip, Alice always chooses the opposite of her flip. B A H H - Bob chooses heads, Win H T - Alice chooses heads, Win T H - Alice chooses tails, Win T T - Bob chooses tails, Win

My experience arriving at this solution made me a bit curious as to how others solved it. Was there reasoning involved before you arrived at a strategy and verified it, or did the strategy just come to you? Did you try multiple strategies, and if so, was there a method to generating/iterating on them, or were they just coming to you and you tried them?

Re: Hello, World

#6

Post by SMackinnon » Mon, May 18, 2015, 2:19 AM UTC

sdab wrote: post #4

SMackinnon wrote: post #3

Spoiler: Bob always chooses the same as his flip, Alice always chooses the opposite of her flip. B A H H - Bob chooses heads, Win H T - Alice chooses heads, Win T H - Alice chooses tails, Win T T - Bob chooses tails, Win

Yep, its a nice problem. Reformulating it such that there are two possibilites (the coins are either different or the same) rather than four (permutations of two coins) is the way to solve the problem. I was going to post a hint rather than the solution, but you beat me to the punch.

Yeah, added a little spoiler tag.

Re: Hello, World

#7

Post by [deleted] » Mon, May 18, 2015, 2:21 AM UTC

SMackinnon wrote: post #3

Spoiler: Bob always chooses the same as his flip, Alice always chooses the opposite of her flip. B A H H - Bob chooses heads, Win H T - Alice chooses heads, Win T H - Alice chooses tails, Win T T - Bob chooses tails, Win

[deleted]

Re: Hello, World

#8

Post by Rangi42 » Mon, May 18, 2015, 2:22 AM UTC

furyofantares wrote: post #5

SMackinnon wrote: post #3

Spoiler: Bob always chooses the same as his flip, Alice always chooses the opposite of her flip. B A H H - Bob chooses heads, Win H T - Alice chooses heads, Win T H - Alice chooses tails, Win T T - Bob chooses tails, Win

My experience arriving at this solution made me a bit curious as to how others solved it. Was there reasoning involved before you arrived at a strategy and verified it, or did the strategy just come to you? Did you try multiple strategies, and if so, was there a method to generating/iterating on them, or were they just coming to you and you tried them?

I made a table of all four possibilities:

    A_coin  B_coin  A_guess  B_guess
    H       H       ?        ?
    H       T       ?        ?
    T       H       ?        ?
    T       T       ?        ?

Then I tried to fill in the guesses, given that A_guess has to be based on B_coin and vice-versa. After making Alice guess the same as her coin flip, since that's a simple thing to try first, it was clear that Bob had to guess the opposite of his coin flip for each row to have exactly one correct match.

Re: Hello, World

#9

Post by SMackinnon » Mon, May 18, 2015, 2:25 AM UTC

furyofantares wrote: post #5

SMackinnon wrote: post #3

Spoiler: Bob always chooses the same as his flip, Alice always chooses the opposite of her flip. B A H H - Bob chooses heads, Win H T - Alice chooses heads, Win T H - Alice chooses tails, Win T T - Bob chooses tails, Win

My experience arriving at this solution made me a bit curious as to how others solved it. Was there reasoning involved before you arrived at a strategy and verified it, or did the strategy just come to you? Did you try multiple strategies, and if so, was there a method to generating/iterating on them, or were they just coming to you and you tried them?

I just thought about what strategies they could actually take without being able to communicate information or use the outcome of the others flip as an input to their decision. There are only a few things you could do- guess either heads or tails every time, guess your roll, or guess the opposite.

Then I realized if one took the "guess same" strategy and the other took the "guess opposite" strategy that would cover the bases.

Re: Hello, World

#10

Post by est » Mon, May 18, 2015, 2:32 AM UTC

This is off topic, but when the next president takes office, all of current whitehouse.gov content will be gone and replaced, no?