Sockets - Riyo

lib/recursive-methods.rb

@@ -1,27 +1,53 @@
 # 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"
+    if n == 0
+        return 1
+    else
+        return n * (factorial(n - 1))
+    end
 end
 
-# Time complexity: ?
-# Space complexity: ?
+# Time complexity: O(n)
+# Space complexity: O(n^2)
 def reverse(s)
-    raise NotImplementedError, "Method not implemented"
+    if s.length <= 1
+        return s
+    end
+    reversed_s = reverse(s[1..-1])
+    reversed_s += s[0]
+    reversed_s
 end
 
-# Time complexity: ?
-# Space complexity: ?
+# Time complexity: O(n)
+# Space complexity: O(n)
 def reverse_inplace(s)
-    raise NotImplementedError, "Method not implemented"
+    i = 0
+    k = s.length - 1
+
+    return helper(s, i, j)
+ end
+
+ def helper(s, i, k)
+     if k <= i
+         return s 
+     end
+
+     temp = s[i]
+     s[i] = s[k]
+     s[k] = temp
+    return helper(s, i + 1, k - 1)
 end
 
-# Time complexity: ?
-# Space complexity: ?
+# Time complexity: O(n)
+# Space complexity: O(n)
 def bunny(n)
-    raise NotImplementedError, "Method not implemented"
+    if n == 0
+        return 0
+    else return 2 + bunny(n-1)
+    end
 end
 
 # Time complexity: ?