Branches C. Gutierrez

lib/recursive-methods.rb

@@ -1,49 +1,117 @@
 # Authoring recursive algorithms. Add comments including time and space complexity for each method.
 
-# Time complexity: ?
-# Space complexity: ?
+# Time complexity: O(n)
+# Space complexity: O(1)
 def factorial(n)
-    raise NotImplementedError, "Method not implemented"
+  if n == 0 || n == 1
+    return 1
+  elsif n < 0
+    raise ArgumentError
+  end
+
+  until n == 1 do
+    return n * factorial(n-1)
+  end
 end
 
-# Time complexity: ?
-# Space complexity: ?
+# Time complexity: O(n)
+# Space complexity: O(1)
 def reverse(s)
-    raise NotImplementedError, "Method not implemented"
+  if s.length <= 1
+    return s
+  end
+
+  reversed_str = reverse(s[1..-1])
+  reversed_str += s[0]
+  reversed_str
 end
 
-# Time complexity: ?
-# Space complexity: ?
+# Time complexity: O(n)
+# Space complexity: O(1)
 def reverse_inplace(s)
-    raise NotImplementedError, "Method not implemented"
+  if s.length <= 1
+    return s
+  end
+
+  return s[s.length-1] + reverse_inplace(s[0, s.length-1])
 end
 
-# Time complexity: ?
-# Space complexity: ?
+# Time complexity: O(n)
+# Space complexity: O(1)
 def bunny(n)
-    raise NotImplementedError, "Method not implemented"
+  if n == 0
+    return 0
+  elsif n == 1
+    return 2
+  else
+    return 2 + bunny(n - 1)
+  end
+
+  return
 end
 
-# Time complexity: ?
-# Space complexity: ?
+# Time complexity: O(n)
+# Space complexity: O(1)
 def nested(s)
-    raise NotImplementedError, "Method not implemented"
+  if s.length.odd?
+    return false
+  elsif
+    s.length == 0
+    return true
+  end
+  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"
+# Time complexity: O(n)
+# Space complexity: O(1)
+
+def search(array,value)
+  if array == []
+    return false
+  elsif array[0] == value
+    return true
+  else
+    array.delete_at(0)
+    return search(array, value)
+  end
 end
 
-# Time complexity: ?
-# Space complexity: ?
+# Time complexity: O(n)
+# Space complexity: O(1)
 def is_palindrome(s)
-    raise NotImplementedError, "Method not implemented"
+  if s.length == 0 || s.length == 1
+    return true
+  elsif s[0] == s[-1]
+    return is_palindrome(s[1..-2])
+  else
+    return false
+  end
 end
 
-# Time complexity: ?
-# Space complexity: ?
-def digit_match(n, m)
-    raise NotImplementedError, "Method not implemented"
+
+
+# Time complexity: O(n + m)
+# Space complexity: O(1)
+
+def digit_match(n, m, c = 0)
+  if n.class != String || m.class != String
+    n = n.to_s
+    m = m.to_s
+  end
+
+  checker = c
+
+  until n.length == 0 || m.length == 0
+    # binding.pry
+    if n[-1] == m[-1]
+      return digit_match(n.chop!, m.chop!, checker + 1)
+    else
+      return digit_match(n.chop!, m.chop!, checker)
+    end
+  end    
+  return checker
 end