Created
April 21, 2010 15:05
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Shuffling an array in Ruby, based on the Array#shuffle! implementation in ruby-1.9
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| =begin | |
| This is the actual C-based implementation of Array#shuffle! in ruby-1.9: | |
| /* | |
| * call-seq: | |
| * array.shuffle! -> array | |
| * | |
| * Shuffles elements in _self_ in place. | |
| */ | |
| static VALUE | |
| rb_ary_shuffle_bang(VALUE ary) | |
| { | |
| long i = RARRAY_LEN(ary); | |
| rb_ary_modify(ary); | |
| while (i) { | |
| long j = rb_genrand_real()*i; | |
| VALUE tmp = RARRAY_PTR(ary)[--i]; | |
| RARRAY_PTR(ary)[i] = RARRAY_PTR(ary)[j]; | |
| RARRAY_PTR(ary)[j] = tmp; | |
| } | |
| return ary; | |
| } | |
| =end | |
| # Non-destructive shuffle | |
| def shuffle(array) | |
| shuffled = array.dup | |
| shuffle!(shuffled) | |
| end | |
| # Here's a basic translation of the C into Ruby | |
| def shuffle!(array) | |
| i = array.size | |
| while i > 0 do | |
| random_index = rand(i) | |
| i -= 1 | |
| temp_val = array[i] | |
| array[i] = array[random_index] | |
| array[random_index] = temp_val | |
| end | |
| array | |
| end | |
| # Let's see if it works | |
| v = [1] | |
| w = [] | |
| x = [1,2,3,4,5,6] | |
| y = ["a","b","c","d"] | |
| z = ["pretty","cool","right"] | |
| puts "#{v} => #{shuffle(v)}" | |
| puts "#{w} => #{shuffle(w)}" | |
| puts "#{x} => #{shuffle(x)}" | |
| puts "#{y} => #{shuffle(y)}" | |
| puts "#{z} => #{shuffle(z)}" |
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