Branches, Kristy

lib/binary.rb

@@ -0,0 +1,46 @@
+def binary_search(array, to_find)
+  high = array.length - 1
+  low = 0
+  while high >= low
+    mid = (high + low) / 2
+    if array[mid] == to_find
+      return mid
+    elsif array[mid] > to_find
+      high = mid - 1
+    else
+      low = mid + 1
+    end
+  end
+
+  return nil
+end
+
+def recursive_binary_search(array, to_find, low = 0, high = array.length - 1)
+  mid = (high + low) / 2
+  return nil if low > high
+  return array[mid] if array[mid] == to_find
+  if to_find < array[mid]
+    return recursive_binary_search(array, to_find, low, mid - 1)
+  else
+    return recursive_binary_search(array, to_find, mid + 1, high)
+  end
+end
+
+class List
+  attr_reader :head, :tail
+
+  def initialize(head, tail)
+    @head = head
+    @tail = tail
+  end
+
+  def self.from_array(array)
+
+  end
+
+  def search(list = self)
+
+  end
+
+
+end

lib/recursive-methods.rb

@@ -1,49 +1,69 @@
 # 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"
+  return 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 || s.empty?
+  return s[-1] + reverse(s[1..-2]) + s[0]
 end
 
-# Time complexity: ?
-# Space complexity: ?
+# Time complexity: O(n) if I had gotten it to work
+# Space complexity: O(n)
 def reverse_inplace(s)
-    raise NotImplementedError, "Method not implemented"
+  return s if s.length == 1 || s.empty? || s[0] == s[-1]
+  while s.length > 0
+    x = s[0]
+    y = s[-1]
+    s[-1] = x
+    s[0] = y
+    return reverse_inplace(s[1..-2])
+  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 >= 1
 end
 
-# Time complexity: ?
-# Space complexity: ?
+# Time complexity: O(n)
+# Space complexity: O(n)
 def nested(s)
-    raise NotImplementedError, "Method not implemented"
+  return true if s.empty?
+  return nested(s[1..-2]) if s[0] == "(" && s[-1] == ")"
+  return false
 end
 
-# Time complexity: ?
-# Space complexity: ?
+# Time complexity: O(n)
+# Space complexity: O(n)
 def search(array, value)
-    raise NotImplementedError, "Method not implemented"
+  return false if array.empty?
+  return true if array[0] == value
+  return search(array[1..-1], value)
 end
 
-# Time complexity: ?
-# Space complexity: ?
+# Time complexity: O(n)
+# Space complexity: O(n)
 def is_palindrome(s)
-    raise NotImplementedError, "Method not implemented"
+  return true if s.empty? || s.length == 1
+  return is_palindrome(s[1..-2])if s[0] == s[-1]
+  return false
 end
 
-# Time complexity: ?
-# Space complexity: ?
+# Time complexity: O(log(n))
+# Space complexity: O(log(n))
 def digit_match(n, m)
-    raise NotImplementedError, "Method not implemented"
-end
+  return 1 if n == 0 && m == 0
+  return 0 if n == 0 || m == 0
+  return 1 if n.digits[0] == 0 && m.digits[0] == 0
+  return 0 + digit_match(n / 10, m / 10) if n % 10 != m % 10
+  return 1 + digit_match(n / 10, m / 10) if n % 10 == m % 10
+end