Ports - Faiza

lib/recursive-methods.rb

@@ -1,27 +1,56 @@
 # Authoring recursive algorithms. Add comments including time and space complexity for each method.
 
-# Time complexity: ?
-# Space complexity: ?
+# Time complexity: O(n) - > the function will run as many times as the given number.
+# Space complexity: O(1) -> we're not creating new variables but the method is taking up space in the stack until the base case equals true, then the stacks will popped of 1 by 1 starting from the top of the stack.
 def factorial(n)
-    raise NotImplementedError, "Method not implemented"
+    # raise NotImplementedError, "Method not implemented"
+    if n < 0
+      raise ArgumentError
+    elsif n == 1 || n == 0
+      return 1
+    end
+    return n * factorial(n - 1)
 end
 
-# Time complexity: ?
-# Space complexity: ?
+def fib(n)
+  if n < 2
+    return n
+  else
+    return fib(n - 1) + fib(n - 2)
+  end
+end
+
+# Time complexity: O(n), where n isnthe length of the input
+# Space complexity: O(1) because additional space in memory is not being consumed 
 def reverse(s)
-    raise NotImplementedError, "Method not implemented"
+  # raise NotImplementedError, "Method not implemented"
+  if s.nil? || s.length == 0 || s.length == 1
+    return s
+  else 
+    return s[-1] + reverse(s[0...-1])
+  end
 end
 
-# Time complexity: ?
-# Space complexity: ?
+# Time complexity: O(n), where n isnthe length of the input
+# Space complexity: O(1) because additional space in memory is not being consumed
 def reverse_inplace(s)
-    raise NotImplementedError, "Method not implemented"
+    # raise NotImplementedError, "Method not implemented"
+    if s.nil? || s.length == 0 || s.length == 1
+      return s
+    else
+      return s[-1] + reverse(s[0...-1]) 
+    end
 end
 
-# Time complexity: ?
-# Space complexity: ?
+# Time complexity: O(n)
+# Space complexity: O(1) because additional space in memory is not being consumed
 def bunny(n)
-    raise NotImplementedError, "Method not implemented"
+  if n == 0 || n.nil?
+    return 0
+    # if 50 is not equal to 100 (50 * 2)
+  else
+    return 2 + bunny(n - 1)
+  end
 end
 
 # Time complexity: ?
@@ -36,14 +65,24 @@ def search(array, value)
     raise NotImplementedError, "Method not implemented"
 end
 
-# Time complexity: ?
-# Space complexity: ?
+# Time complexity: O(n) where n is the size of the input
+# Space complexity: O(1) because additional space in memory is not being consumed
 def is_palindrome(s)
-    raise NotImplementedError, "Method not implemented"
+  # raise NotImplementedError, "Method not implemented"
+  if s.nil? || s.length == 0 || s.length == 1
+    return true
+  else
+    if s[0] == s[-1]
+      is_palindrome(s[1..-2])
+    else
+      return false
+    end
+  end
 end
 
 # Time complexity: ?
 # 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
@@ -260,7 +260,7 @@
     end      
 end
 
-xdescribe "is_palindrome" do
+describe "is_palindrome" do
   it "will return true for emptystring" do
     # Arrange
     string = ""