Branches -- Paige D.

lib/recursive-methods.rb

@@ -1,49 +1,73 @@
 # Authoring recursive algorithms. Add comments including time and space complexity for each method.
 
-# Time complexity: ?
-# Space complexity: ?
+# Time complexity: O(n)
+# Space complexity: O(n)
 def factorial(n)
-    raise NotImplementedError, "Method not implemented"
+  raise ArgumentError if n < 0
+  return 1 if n == 1 || n == 0
+  return n * factorial(n-1) if n > 1
 end
 
-# Time complexity: ?
-# Space complexity: ?
+# Time complexity: O(n)
+# Space complexity: O(n)
 def reverse(s)
-    raise NotImplementedError, "Method not implemented"
+  return s if s.length <= 1
+  return s[-1] + reverse(s[1..-2]) + s[0]
 end
 
-# Time complexity: ?
-# Space complexity: ?
-def reverse_inplace(s)
-    raise NotImplementedError, "Method not implemented"
+# Time complexity: O(n)
+# Space complexity: O(n)
+def reverse_inplace(s, i = 0, j = s.length - 1)
+  if i >= j
+    return s
+  else
+    x = s[j]
+    y = s[i]
+    s[i] = x
+    s[j] = y
+    reverse_inplace(s, i += 1, j -= 1)
+  end
 end
 
-# Time complexity: ?
-# Space complexity: ?
+# Time complexity: O(n)
+# Space complexity: O(n)
 def bunny(n)
-    raise NotImplementedError, "Method not implemented"
+  return 0 if n == 0
+  return 2 + bunny(n - 1) if n > 0
 end
 
-# Time complexity: ?
-# Space complexity: ?
+# Time complexity: O(n)
+# Space complexity: O(n)
 def nested(s)
-    raise NotImplementedError, "Method not implemented"
+  return false if s.length.odd?
+  return true if s.length == 0
+  return false if s[0] != "(" || s[-1] != ")"
+  return nested(s[1..-2]) if s.length > 0
 end
 
-# Time complexity: ?
-# Space complexity: ?
-def search(array, value)
-    raise NotImplementedError, "Method not implemented"
+# Time complexity: o(n)
+# Space complexity: O(n)
+def search(array, value, i = 0)
+  return false if i == array.length
+  return true if array[i] == value
+  return search(array, value, i += 1)
 end
 
-# Time complexity: ?
-# Space complexity: ?
-def is_palindrome(s)
-    raise NotImplementedError, "Method not implemented"
+# Time complexity: O(n)
+# Space complexity: O(n)
+def is_palindrome(s, start_index = 0, last_index = s.length - 1)
+  return false if s[start_index] != s[last_index]
+  return true if start_index > last_index
+  return is_palindrome(s, start_index += 1, last_index -= 1)
 end
 
-# Time complexity: ?
-# Space complexity: ?
-def digit_match(n, m)
-    raise NotImplementedError, "Method not implemented"
-end
+# Time complexity: O(n) - where n is the number with less digits
+# Space complexity: O(n) - where n is the number with less digits
+def digit_match(n, m, match_count = 0)
+  n = n.to_s
+  m = m.to_s
+
+  return match_count if n[-1] == nil || m[-1] == nil
+  return digit_match(n[0..-2], m[0..-2], match_count += 1) if n[-1] == m[-1]
+  return digit_match(n[0..-2], m[0..-2], match_count)
+end

test/recursion_writing_test.rb

@@ -3,6 +3,7 @@
 require "minitest/skip_dsl"
 require_relative '../lib/recursive-methods'
 
+
 describe "factorial" do
   it "will find the factorial of 0" do
     # Arrange
@@ -33,12 +34,12 @@
 
     # Act-Assert
     expect {
-      answer = factorial(num)
+      factorial(num)
     }.must_raise ArgumentError
   end
 end
 
-xdescribe "reverse" do
+describe "reverse" do
   it "will reverse 'cat'" do
     # Arrange
     string = "cat"
@@ -84,52 +85,52 @@
 end
 
 
-xdescribe "reverse_in_place" do
+describe "reverse_in_place" do
   it "will reverse 'cat'" do
     # Arrange
     string = "cat"
 
     # Act
-    answer = reverse_inplace(string)
+    reverse_inplace(string)
 
     # Assert
-    expect(answer).must_equal "tac"
+    expect(string).must_equal "tac"
   end
 
   it "will reverse 'a'" do
     # Arrange
     string = "a"
 
     # Act
-    answer = reverse_inplace(string)
+    reverse_inplace(string)
 
     # Assert
-    expect(answer).must_equal "a"
+    expect(string).must_equal "a"
   end
 
   it "will reverse empty string " do
     # Arrange
     string = ""
 
     # Act
-    answer = reverse_inplace(string)
+    reverse_inplace(string)
 
     # Assert
-    expect(answer).must_equal ""
+    expect(string).must_equal ""
   end
   it "will reverse 'apple'" do
     # Arrange
     string = "apple"
 
     # Act
-    answer = reverse_inplace(string)
+    reverse_inplace(string)
 
     # Assert
-    expect(answer).must_equal "elppa"
+    expect(string).must_equal "elppa"
   end
 end
 
-xdescribe "bunny" do
+describe "bunny" do
   it "returns 0 for 0 bunnies" do
     # Arrange
     count = 0
@@ -164,8 +165,8 @@
   end
 end
 
-xdescribe "nested" do
-  it "will return true for empystring" do
+describe "nested" do
+  it "will return true for empty string" do
     # Arrange
     string = ""
 
@@ -210,7 +211,7 @@
   end
 end
 
-xdescribe "search" do
+describe "search" do
   it "will return false for empty array" do
     # Arrange
     item = "a"
@@ -260,7 +261,7 @@
     end      
 end
 
-xdescribe "is_palindrome" do
+describe "is_palindrome" do
   it "will return true for emptystring" do
     # Arrange
     string = ""
@@ -295,7 +296,7 @@
   end
 end
 
-xdescribe "digit_match" do
+describe "digit_match" do
   it "returns 4 for 1072503891 and 62530841" do
     # Arrange
     num1 = 1072503891