Data commit

Task/Knuth-shuffle/Eiffel/knuth-shuffle.e

@@ -0,0 +1,55 @@
+class
+	APPLICATION
+
+create
+	make
+
+feature {NONE} -- Initialization
+
+	make
+		do
+			test := <<1, 2>>
+			io.put_string ("Initial: ")
+			across
+				test as t
+			loop
+				io.put_string (t.item.out + " ")
+			end
+			test := shuffle (test)
+			io.new_line
+			io.put_string ("Shuffled: ")
+			across
+				test as t
+			loop
+				io.put_string (t.item.out + " ")
+			end
+		end
+
+	test: ARRAY [INTEGER]
+
+	shuffle (ar: ARRAY [INTEGER]): ARRAY [INTEGER]
+			-- Array containing the same elements as 'ar' in a shuffled order.
+		require
+			more_than_one_element: ar.count > 1
+		local
+			count, j, ith: INTEGER
+			random: V_RANDOM
+		do
+			create random
+			create Result.make_empty
+			Result.deep_copy (ar)
+			count := ar.count
+			across
+				1 |..| count as c
+			loop
+				j := random.bounded_item (c.item, count)
+				ith := Result [c.item]
+				Result [c.item] := Result [j]
+				Result [j] := ith
+				random.forth
+			end
+		ensure
+			same_elements: across ar as a all Result.has (a.item) end
+		end
+
+end