Ruby - returns an array in random order

Question

What is the easiest way to return an array randomly in Ruby? Anything good and short that can be used in an IRB session, for example

[1,2,3,4,5].random() # or random_sort([1,2,3,4,5]) 

Answer 1

If you do not have [] .shuffle, [] .sort_by {rand} works, as indicated by sepp2k..sort_by temporarily replaces each element with something to sort, in this case a random number.

[]. sort {rand-0.5}, however, will not move correctly. Some languages ​​(for example, some Javascript implementations) do not shuffle arrays if you randomly sort by array, and sometimes quite public ones.

JS analysis (with graphs!): Http://www.robweir.com/blog/2010/02/microsoft-random-browser-ballot.html

Ruby is no different! This problem has the same problem. :)

 #sort a bunch of small arrays by rand-0.5 a=[] 100000.times{a << [0,1,2,3,4].sort{rand-0.5}} #count how many times each number occurs in each position b=[] a.each do |x| x.each_index do |i| b[i] ||=[] b[i][x[i]] ||= 0 b[i][x[i]] += 1 end end pb 

=>

 [[22336, 18872, 14814, 21645, 22333], [17827, 25005, 20418, 18932, 17818], [19665, 15726, 29575, 15522, 19512], [18075, 18785, 20283, 24931, 17926], [22097, 21612, 14910, 18970, 22411]] 

Each element should appear in each position about 20,000 times. [] .sort_by (rand) gives much better results.

 #sort with elements first mapped to random numbers a=[] 100000.times{a << [0,1,2,3,4].sort_by{rand}} #count how many times each number occurs in each position ... 

=>

 [[19913, 20074, 20148, 19974, 19891], [19975, 19918, 20024, 20030, 20053], [20028, 20061, 19914, 20088, 19909], [20099, 19882, 19871, 19965, 20183], [19985, 20065, 20043, 19943, 19964]] 

Similarly for [] .shuffle (which is probably the fastest)

 [[20011, 19881, 20222, 19961, 19925], [19966, 20199, 20015, 19880, 19940], [20062, 19894, 20065, 19965, 20014], [19970, 20064, 19851, 20043, 20072], [19991, 19962, 19847, 20151, 20049]] 

Answer 2

array.shuffle

Answer 3

How about this?

Helper methods for Enumerable, Array, Hash and String that allows you to select a random item or shuffle the order of elements.

http://raa.ruby-lang.org/project/rand/