Sara-Branches

lib/recursive-methods.rb

@@ -1,49 +1,101 @@
 # Authoring recursive algorithms. Add comments including time and space complexity for each method.
 
-# Time complexity: ?
-# Space complexity: ?
+# Time complexity: 0(n)
+# Space complexity: 0(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)
 end
 
-# Time complexity: ?
-# Space complexity: ?
+# Time complexity: 0(n)
+# Space complexity: 0(n)
 def reverse(s)
-    raise NotImplementedError, "Method not implemented"
+
+    return s if s.length < 2
+    return reverse(s[1..-1])  + s[0]
+
 end
 
 # Time complexity: ?
 # Space complexity: ?
 def reverse_inplace(s)
-    raise NotImplementedError, "Method not implemented"
+    return s if s.length == 0
+    return reverse(s[1..-1]) + s[0]
 end
 
 # Time complexity: ?
 # Space complexity: ?
 def bunny(n)
-    raise NotImplementedError, "Method not implemented"
+    return 0 if n == 0
+    return 2 if n == 1
+    return bunny(n - 1) + bunny(1)
+
 end
 
+
 # Time complexity: ?
 # Space complexity: ?
 def nested(s)
-    raise NotImplementedError, "Method not implemented"
+    # return nested_helper(s[1..-1])
+    paren_end = s.index(')')
+    return !s.include?('(') if paren_end.nil? 
+
+    paren_start = s[0...paren_end].rindex('(')
+
+    return false if paren_start.nil?
+
+    return nested(s[1..paren_start]+s[paren_end+1..-1])
+
+end
+
+def nested_helper(s)
+    return true if s.empty?
+    return false if s.length.odd?
+    return nested_helper(s)
 end
 
 # Time complexity: ?
 # Space complexity: ?
 def search(array, value)
-    raise NotImplementedError, "Method not implemented"
+    return false if array.nil?
+    return true if array[0] == value
+    return search(array[1..-1],value)
 end
 
 # Time complexity: ?
 # Space complexity: ?
 def is_palindrome(s)
-    raise NotImplementedError, "Method not implemented"
+    return true if s.empty? || s.length ==1
+    return false if s[0] != s[s.length - 1]
+    return is_palindrome_helper(s, 1)
+
+end
+
+def is_palindrome_helper(s, index)
+    return true if s.empty? || s.length ==1
+    return false if s[0] != s[s.length - index]
+    is_palindrome_helper(s[1..s.length - index - 1], 1)
+
 end
 
 # Time complexity: ?
 # Space complexity: ?
 def digit_match(n, m)
-    raise NotImplementedError, "Method not implemented"
+
+    return 1 if n == 0 && m == 0 
+    count = 0
+    if n % 10 == m % 10
+        count += 1
+    end
+    if (n / 10 == 0 || m / 10 == 0) 
+        return count
+    end
+
+    return count + digit_match(n / 10, m / 10)
+
+end
+
+def digit_match_helper(n, m)
+
 end

test/recursion_writing_test.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
@@ -164,7 +164,7 @@
   end
 end
 
-xdescribe "nested" do
+describe "nested" do
   it "will return true for empystring" do
     # Arrange
     string = ""
@@ -210,7 +210,7 @@
   end
 end
 
-xdescribe "search" do
+describe "search" do
   it "will return false for empty array" do
     # Arrange
     item = "a"
@@ -260,7 +260,7 @@
     end      
 end
 
-xdescribe "is_palindrome" do
+describe "is_palindrome" do
   it "will return true for emptystring" do
     # Arrange
     string = ""
@@ -295,7 +295,7 @@
   end
 end
 
-xdescribe "digit_match" do
+describe "digit_match" do
   it "returns 4 for 1072503891 and 62530841" do
     # Arrange
     num1 = 1072503891