Data commit

Task/Happy-numbers/Eiffel/happy-numbers.e

@@ -0,0 +1,70 @@
+class
+	APPLICATION
+
+create
+	make
+
+feature {NONE} -- Initialization
+
+	make
+			-- Run application.
+		local
+			l_val: INTEGER
+		do
+			from
+				l_val := 1
+			until
+				l_val > 100
+			loop
+				if is_happy_number (l_val) then
+					print (l_val.out)
+					print ("%N")
+				end
+				l_val := l_val + 1
+			end
+		end
+
+feature -- Happy number
+
+	is_happy_number (a_number: INTEGER): BOOLEAN
+			-- Is `a_number' a happy number?
+		require
+			positive_number: a_number > 0
+		local
+			l_number: INTEGER
+			l_set: ARRAYED_SET [INTEGER]
+		do
+			from
+				l_number := a_number
+				create l_set.make (10)
+			until
+				l_number = 1 or l_set.has (l_number)
+			loop
+				l_set.put (l_number)
+				l_number := square_sum_of_digits (l_number)
+			end
+
+			Result := (l_number = 1)
+		end
+
+feature{NONE} -- Implementation
+
+	square_sum_of_digits (a_number: INTEGER): INTEGER
+			-- Sum of the sqares of digits of `a_number'.
+		require
+			positive_number: a_number > 0
+		local
+			l_number, l_digit: INTEGER
+		do
+			from
+				l_number := a_number
+			until
+				l_number = 0
+			loop
+				l_digit := l_number \\ 10
+				Result := Result + l_digit * l_digit
+				l_number := l_number // 10
+			end
+		end
+
+end