Ports - Ari (in progress!)

lib/recursive-methods.rb

@@ -1,27 +1,50 @@
 # Authoring recursive algorithms. Add comments including time and space complexity for each method.
 
-# Time complexity: ?
-# Space complexity: ?
+# Time complexity: O(n), where n is the value of the number
+# Space complexity: O(n), where n is the value of the number
 def factorial(n)
-    raise NotImplementedError, "Method not implemented"
+  if n == 0
+    return 1
+  elsif n.nil? || n < 0
+    raise ArgumentError, "This value is not valid."
+  end
+
+  return n * factorial(n-1)
+
 end
 
-# Time complexity: ?
-# Space complexity: ?
+# Time complexity: O(n), where n is the length of the string
+# Space complexity: O(n), because there will be n layers to the call stack.
 def reverse(s)
-    raise NotImplementedError, "Method not implemented"
+
+    if s.length == 0
+      return s
+    else 
+      return s[s.length-1] + reverse(s[0, s.length-1])
+    end
+
 end
 
-# Time complexity: ?
-# Space complexity: ?
+# Time complexity: O(n), where n is the length of the string
+# Space complexity: O(n), because there will be n layers to the call stack.
 def reverse_inplace(s)
-    raise NotImplementedError, "Method not implemented"
+
+  if s.length == 0
+    return s
+  else 
+    return s[s.length-1] + reverse(s[0, s.length-1])
+  end
+
 end
 
 # Time complexity: ?
 # Space complexity: ?
 def bunny(n)
-    raise NotImplementedError, "Method not implemented"
+    if n % 2 == 0
+      return 0
+    else
+      return n + bunny(2-1)
+    end
 end
 
 # Time complexity: ?
@@ -46,4 +69,4 @@ def is_palindrome(s)
 # Space complexity: ?
 def digit_match(n, m)
     raise NotImplementedError, "Method not implemented"
-end
+end

specs/recursion_writing_spec.rb

@@ -38,7 +38,7 @@
   end
 end
 
-xdescribe "reverse" do
+describe "reverse" do
   it "will reverse 'cat'" do
     # Arrange
     string = "cat"
@@ -84,7 +84,7 @@
 end
 
 
-xdescribe "reverse_in_place" do
+describe "reverse_in_place" do
   it "will reverse 'cat'" do
     # Arrange
     string = "cat"
@@ -129,7 +129,7 @@
   end
 end
 
-xdescribe "bunny" do
+describe "bunny" do
   it "returns 0 for 0 bunnies" do
     # Arrange
     count = 0
@@ -331,4 +331,4 @@
      # Assert
      expect(answer).must_equal 3
   end
-end
+end