new files

Task/Knuth-shuffle/Ruby/knuth-shuffle-1.rb

@@ -0,0 +1,21 @@
+class Array
+  def knuth_shuffle!
+    j = length
+    i = 0
+    while j > 1
+      r = i + rand(j)
+      self[i], self[r] = self[r], self[i]
+      i += 1
+      j -= 1
+    end
+    self
+  end
+end
+
+r = Hash.new(0)
+100_000.times do |i|
+  a = [1,2,3].knuth_shuffle!
+  r[a] += 1
+end
+
+r.keys.sort.each {|a| puts "#{a.inspect} => #{r[a]}"}

Task/Knuth-shuffle/Ruby/knuth-shuffle-2.rb

@@ -0,0 +1,9 @@
+class Array
+  def knuth_shuffle!
+    (length - 1).downto(1) do |i|
+      j = rand(i + 1)
+      self[i], self[j] = self[j], self[i]
+    end
+    self
+  end
+end