Leaves - Emily V

lib/fibonacci.rb

@@ -1,8 +1,18 @@
 # Improved Fibonacci
+# Time Complexity - O(n)
+# Space Complexity - O(n)
 
-# Time Complexity - ?
-# Space Complexity - ?  (should be O(n))
-# Hint, you may want a recursive helper method
 def fibonacci(n)
-
+  return fib_helper(0, 1, 2, n)
 end
+
+def fib_helper(fib_minus_two, fib_minus_one, current, n)
+  return n if n == 0 || n == 1
+  raise ArgumentError if n < 0
+
+  if current == n
+    return fib_minus_one + fib_minus_two
+  end 
+
+  return fib_helper(fib_minus_one, fib_minus_one + fib_minus_two, current + 1, n)
+end 

lib/super_digit.rb

@@ -1,15 +1,38 @@
 # Superdigit
 
-# Time Complexity - ?
-# Space Complexity - ?
+# Time Complexity - O(1) <- this doesn't feel quite right but it's definitely not O(n)
+# Space Complexity - O(1) <- same here
 def super_digit(n)
-   
+  return super_digit_helper(n.to_s)
 end
+
+def super_digit_helper(n)
+  return n.to_i if n.length == 1 
+
+  sum = 0
+  n.each_char do |digit|
+    sum += digit.to_i
+  end 
+
+  return super_digit_helper(sum.to_s)
+end 
 
+# Time Complexity - O(1) <- same qualms as above
+# Space Complexity - O(1)
+# I think I missed the point here, this doesn't seem like it would necessarily involve more time complexity than regular super_digit so I'm not sure how to reduce it
 
-# Time Complexity - ?
-# Space Complexity - ?
 def refined_super_digit(n, k)
-
+  return refined_super_digit_helper(n.to_s * k)
+end
+
+def refined_super_digit_helper(n)
+  return n.to_i if n.length == 1 
+
+  sum = 0
+  n.each_char do |digit|
+    sum += digit.to_i
+  end 
+
+  return super_digit_helper(sum.to_s)
 end
 

test/super_digit_test.rb

@@ -1,6 +1,6 @@
 require_relative "test_helper"
 
-xdescribe "super_digit" do
+describe "super_digit" do
   it "will return 2 for super_digit(9875)" do
     # Act
     answer = super_digit(9875)