Leaves - Julia K

lib/fibonacci.rb

@@ -1,8 +1,25 @@
 # Improved Fibonacci
 
-# Time Complexity - ?
-# Space Complexity - ?  (should be O(n))
-# Hint, you may want a recursive helper method
+# Time Complexity - O(n) because it performs n operations
+# Space Complexity - O(n) because it makes n calls on the stack
+
 def fibonacci(n)
-
+  return fib_helper(n, n_minus_2 = 0, n_minus_1 = 1, 2)
 end
+
+def fib_helper(n, n_minus_2, n_minus_1, current) # starting values (4, 0, 1, 2)
+
+  # base cases
+
+  raise ArgumentError if n < 0
+  return n if n == 0 || n == 1
+  return n_minus_1 + n_minus_2 if current == n
+
+  # recursive step -- increment current and reassign n_minus_2 and n_minus_1
+  current += 1 
+  fibber = n_minus_1 
+  n_minus_1 = n_minus_1 + n_minus_2 
+  n_minus_2 = fibber 
+  return fib_helper(n, n_minus_2, n_minus_1, current)   
+end
+

lib/super_digit.rb

@@ -1,15 +1,21 @@
 # Superdigit
 
-# Time Complexity - ?
-# Space Complexity - ?
-def super_digit(n)
-
+# Time Complexity - O log n because with each operation we are cutting the total of n by at worst 10
+# Space Complexity - O log n
+def super_digit(n) 
+  # base case
+  if n <= 9
+    return n
+  else
+    # recursive step -- convert number to array of integers and add them all together
+    n_array = n.digits
+    n = n_array.sum
+    super_digit(n)
+  end
 end
-
 
 # Time Complexity - ?
 # Space Complexity - ?
 def refined_super_digit(n, k)
-    
+
 end
-

test/fibonacci_test.rb

@@ -41,10 +41,10 @@
   end
   it "will return 5 for fib(5)" do
     # Act
-    answer = fibonacci(4)
+    answer = fibonacci(5)
 
     # Assert
-    expect(answer).must_equal 3
+    expect(answer).must_equal 5
   end
   it "will return 55 for fib(10)" do
     # Act

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)
@@ -33,7 +33,7 @@
     expect(answer).must_equal 6
   end
 
-  describe "refined superdigit" do 
+  xdescribe "refined superdigit" do 
     it "will return 1 for n = 1 and k = 1" do
       # Act
       answer = refined_super_digit(1, 1)