I have a series of random numbers for a lottery.
How can i chose the random number for the second place and so on, without having the risk of pulling out the first place again?
$first = rand(0..99999) $second = rand(0..99999) $third = rand(0..99999) I need to get some sort of exception in the following drawings.
shuffle will permute the entire array, which is potentially slow for large arrays. sample is a much faster operation
(1..99999).to_a.sample(3) For benchmarking purposes:
> require 'benchmark' > arr = (0..99999).to_a; 0 > Benchmark.realtime { 10_000.times { arr.sample(3) } } => 0.002874 > Benchmark.realtime { 10_000.times { arr.shuffle[0,3] } } => 18.107669 
If you are picking out a very small number of numbers from a large array it might be smart to just get 3 random numbers and the check that they are different:
def create_array_and_pick_three arr = (0..99999).to_a arr.sample(3) end def get_three_random_until_uniq array, num = [], 3 array = (1..num).map{rand(0..99999)} until array.uniq.size == num end p Benchmark.realtime { 1000.times { create_array_and_pick_three }} #=> 4.343435 p Benchmark.realtime { 1000.times { get_three_random_until_uniq }} #=> 0.002 Exactly what is faster for you depends on the size of the array and the number of random numbers you need.
