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What resources can I use if I'm trying to settle a coin flip online? Obviously, a coin toss app won't work if it only displays the result to me - the other party should also see it. And we can't meet up in person. Sharing screens came to mind, but I was wondering if there's some session sharing website that handles things like this.

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closed as off topic by soandos, Dave M, iglvzx, Diogo, nhinkle Apr 3 '12 at 2:54

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How about a checkmark, or series of checkmarks, then divide by 23, multiply for 49, minus 4, convert to binary, take the 1's and 0's and put them into base ten, divide by 2.5, stand on one leg, and choose left or right mouse click? If it's even, it's heads, odd, it's tails –  Canadian Luke Apr 2 '12 at 23:27
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Play any two-player game where the result is random as opposed to skill-based? –  Tom Wijsman Apr 2 '12 at 23:41
    
^ like card or dice online games and use first card, high card, or first roll etc –  Psycogeek Apr 2 '12 at 23:59
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Depending on how long you are prepared to wait, you could use tomorrows lottery numbers. If the first ball is less then half the max value, player 1 wins, if it is greater than half, player 2 wins. –  Paul Apr 3 '12 at 0:13

2 Answers 2

up vote 5 down vote accepted

There's a site at http://flipfor.us/ that will allow you to flip a coin and it will email the result to you and your opponent. For a one-off, it's useful

I'd consider building a site that allows two users to log in and flip coins together, but I have way too many little projects already. :P

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One problem with flipfor.us is that the confirmation email of who appears to have come from your opponent, so it would be easy from them to generate a spoof email. –  Garrett Jun 16 at 1:29
    
Other options include cointossr.com and flipacoinonline.com. They both seem to be ungameable. –  Garrett Jun 16 at 1:32

You could create a shared Google Docs spreadsheet and enter this into one of the cells:

=ROUND(RAND())

Or...

=IF(ROUND(RAND()), "Joe", "Sally")

Every time you save (or rather Google Docs autosaves), the random number generator will generate a new number. So to do a coin toss just type a random character into any (other) cell and hit enter. Both users will see the same result.


Some not so simple but more interesting solutions...

You could try generating 2 random stock symbols:

CONCATENATE(
  CHAR(RANDBETWEEN(65,90)),
  CHAR(RANDBETWEEN(65,90)),
  CHAR(RANDBETWEEN(65,90))
)

and use GoogleFinance(..., "price") to look up which is higher. Sort of a Wall Street high card draw...

However, do not combine both formulas in one cell, because this will cause an infinite loop: GoogleFinance() will fetch the stock price, changing the spreadsheet, causing the RANDBETWEEN() functions to recalculate, causing the stock symbol to be changed, causing GoogleFinance() to fetch a new value...

You can however, automate this process safely by using JavaScript (Google Apps Script) to generate the random letters.

You can also use Google Apps Script to track the number of times the random number generator has been run in the first solution to prevent cheating (or simply modify the formula to insert a neutral value as a simple binary counter).


Another solution would be to take a random word or string, add the CODE() value of each character, and select the least significant bit. If you're really paranoid, have one person pick the string, and have the other pick which bit position to use.

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very simple, thanks! –  Aram Kocharyan Apr 3 '12 at 2:02

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