Help making random function faster

[MaxGeek]

So I have a method that randomly places pieces on a board. The method uses the rejection method where it will create a random number to place the piece on the board, but if the place is already taken it will try again. The problem with this method is that if I have a lot of pieces to place it is very slow. (Like 40 pieces and 50 spaces)

How can I make this kind of method run faster no matter how many pieces or spaces there are?

 

[MaxGeek]

Forget it, I think I've figured out a way to do it.

 

[sedj]

I would keep a list of all the available spaces - then use the random number to select one of the available numbers/spaces (ie like a subscript in an array) - keeping the random number below the number of actual spaces left - so you don't ever actually check if a space is taken, because you always generate a number for a space that exists.

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