water - marj

.gitignore

@@ -0,0 +1,2 @@
+.idea/
+.rakeTasks

lib/recursive-methods.rb

@@ -1,49 +1,115 @@
 # Authoring recursive algorithms. Add comments including time and space complexity for each method.
 
-# Time complexity: ?
-# Space complexity: ?
+# Time complexity: n
+# Space complexity: n
 def factorial(n)
-    raise NotImplementedError, "Method not implemented"
+    raise ArgumentError if n < 0
+    return 1 if n == 0
+    return 1 if n == 1
+    return n * factorial(n - 1)
 end
 
-# Time complexity: ?
-# Space complexity: ?
-def reverse(s)
-    raise NotImplementedError, "Method not implemented"
+# Time complexity: n^2
+# Space complexity: n^2
+def reverse(s) #was the answer to this supposed to be different from the one below??
+    if s.length == 0
+        return s
+    else
+        return reverse(s[1..-1]) +s[0]
+    end
 end
 
-# Time complexity: ?
-# Space complexity: ?
+# Time complexity: n
+# Space complexity: n
 def reverse_inplace(s)
-    raise NotImplementedError, "Method not implemented"
+    #fix - add a few default arguments
+    #add optional arguments
+    if s.length == 0
+        return s
+    else
+        return reverse(s[1..-1]) + s[0]
+    end
+
+    #Try Iterator to Recusion...
+    # reverse_index = -1
+    # count = 0
+    # length = s.length
+    #
+    # while count < length / 2
+    #     temp = s[count]
+    #     s[count] = s[reverse_index]
+    #     s[reverse_index] = temp
+    #
+    #     count += 1
+    #     reverse_index -= 1
+    # end
+    # return s
 end
 
-# Time complexity: ?
-# Space complexity: ?
+#***
+# Could not for the life of me
+# figure out how to do this recursively based
+# on the tests provided.
+# Didn't even use a loop to convert...>_<
+#***
+# Time complexity: n
+# Space complexity: n
 def bunny(n)
-    raise NotImplementedError, "Method not implemented"
+    return 0 if n == 0
+    if n > 0
+        return  bunny(n - 1) + 2
+    end
 end
 
-# Time complexity: ?
-# Space complexity: ?
+# Time complexity: n^2
+# Space complexity: n^2
 def nested(s)
-    raise NotImplementedError, "Method not implemented"
+    return true if s.length == 0
+    return false if s.length % 2 != 0
+    if s[0] != s[-1]
+        return nested(s[1..-2])
+    else
+        return false
+    end
 end
 
+
 # Time complexity: ?
 # Space complexity: ?
 def search(array, value)
-    raise NotImplementedError, "Method not implemented"
+    return false if array.length == 0
+    if array[0] == value
+        return true
+    else
+        return search(array[1..-1], value)
+    end
 end
 
-# Time complexity: ?
-# Space complexity: ?
+# Time complexity: n
+# Space complexity: n
 def is_palindrome(s)
-    raise NotImplementedError, "Method not implemented"
+    return true if s.length == 0
+    if s[0] == s[-1]
+        return is_palindrome(s[1..-2])
+    else
+        return false
+    end
 end
 
-# Time complexity: ?
-# Space complexity: ?
+# Time complexity: n
+# Space complexity: n
+#
+# how many calls
+# how expensive is each call
 def digit_match(n, m)
-    raise NotImplementedError, "Method not implemented"
+    if n < 10 || m < 10
+        last_digit_m = m % 10
+        last_digit_n = n % 10
+        return last_digit_m == last_digit_n ? 1 : 0
+    else
+        last_digit_m = m % 10
+        last_digit_n = n % 10
+        match = last_digit_m == last_digit_n ? 1 : 0
+        return digit_match(n / 10, m / 10) + match
+    end
 end

test/recursion_writing_test.rb

@@ -167,8 +167,8 @@
   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 = ""
 
@@ -213,7 +213,7 @@
   end
 end
 
-xdescribe "search" do
+describe "search" do
   it "will return false for empty array" do
     # Arrange
     item = "a"
@@ -263,7 +263,7 @@
     end      
 end
 
-xdescribe "is_palindrome" do
+describe "is_palindrome" do
   it "will return true for emptystring" do
     # Arrange
     string = ""
@@ -298,7 +298,7 @@
   end
 end
 
-xdescribe "digit_match" do
+describe "digit_match" do
   it "returns 4 for 1072503891 and 62530841" do
     # Arrange
     num1 = 1072503891
@@ -311,7 +311,7 @@
     expect(answer).must_equal 4
   end
 
-  it "returns 0 for nonmatching numbers" do
+  it "returns 0 for non matching numbers" do
     # Arrange
     num1 = 0
     num2 = 62530841
@@ -358,4 +358,24 @@
     # Assert
     expect(answer).must_equal 1
   end
+
+  it "returns 0 for (107, 6)" do
+    # Arrange
+
+    # Act
+    expect(digit_match(107, 6)).must_equal 0
+    expect(digit_match(6, 107)).must_equal  0
+    expect(digit_match(0, 0)).must_equal 1
+    expect(digit_match(2, 2)).must_equal 1
+    expect(digit_match(7, 6)).must_equal 0
+    expect(digit_match(10, 0)).must_equal 1
+    expect(digit_match(10, 1)).must_equal 0
+
+    expect(digit_match(1007, 16)).must_equal 0
+    expect(digit_match(1007, 27)).must_equal 1
+
+
+    # Assert
+    # expect(answer).must_equal 0
+  end
 end