perplexus.info :: Algorithms : More randomness!

More randomness! (Posted on 2003-06-30)

Suppose you have a function (or a magic ball) that is capable of producing a totally random integer between 1 and 5 (inclusive).

Using this, how would you generate a random number (also an integer) between 1 and 7 (inclusive)? (Note that the for the number to be random, all integers between 1 and 7 must have an equal chance of being generated)

Assume that using your 1-5 generator is pretty time-consuming, so you want to minimize the number of times you are going to use it.

Submitted by levik

Rating: 4.4286 (7 votes)

Solution: (Hide)

A number of solutions submitted in the comments solve the problem.
Friedlinguini's solution here does so only calling the original function less than 3 times on average.

Comments: ( You must be logged in to post comments.)

Subject	Author	Date
re: A binary solution	S	2003-10-31 00:22:11
A binary solution	Federico Kereki	2003-07-14 15:49:01
Another look at optimality	friedlinguini	2003-07-01 06:55:26
re(5): solution	friedlinguini	2003-07-01 05:56:59
re(4): solution	Charlie	2003-07-01 05:38:24
re(3): solution	friedlinguini	2003-07-01 05:17:58
re(2): solution	Charlie	2003-06-30 15:14:41
re: solution	Gamer	2003-06-30 13:26:10
re(2): Quick and Dirty Solution	friedlinguini	2003-06-30 09:12:31
Optimal Solution	friedlinguini	2003-06-30 09:04:07
solution	Charlie	2003-06-30 08:52:22
re: Quick and Dirty Solution	Charlie	2003-06-30 08:50:42
re: Possible Solution	friedlinguini	2003-06-30 08:05:55
Possible Solution	derek	2003-06-30 07:52:56
impossible?	Travis Taylor	2003-06-30 06:59:30
Quick and Dirty Solution	friedlinguini	2003-06-30 06:56:18

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