Maha- Earth -Recursive methods

Gemfile.lock

@@ -0,0 +1,36 @@
+GEM
+  remote: https://rubygems.org/
+  specs:
+    ansi (1.5.0)
+    builder (3.2.4)
+    coderay (1.1.3)
+    method_source (1.0.0)
+    minitest (5.14.2)
+    minitest-reporters (1.4.2)
+      ansi
+      builder
+      minitest (>= 5.0)
+      ruby-progressbar
+    minitest-skip (0.0.3)
+      minitest (~> 5.0)
+    minitest-spec (0.0.2.1)
+      minitest (>= 3.0)
+    pry (0.13.1)
+      coderay (~> 1.1)
+      method_source (~> 1.0)
+    rake (13.0.1)
+    ruby-progressbar (1.10.1)
+
+PLATFORMS
+  ruby
+
+DEPENDENCIES
+  minitest
+  minitest-reporters
+  minitest-skip
+  minitest-spec
+  pry
+  rake
+
+BUNDLED WITH
+   2.1.4

lib/recursive-methods.rb

@@ -3,47 +3,92 @@
 # Time complexity: ?
 # Space complexity: ?
 def factorial(n)
-    raise NotImplementedError, "Method not implemented"
+    raise ArgumentError if n < 0
+    if n == 0
+        return 1
+    else
+        return n * factorial(n-1)
+    end
 end
 
-# Time complexity: ?
-# Space complexity: ?
+# Time complexity: O(n^2)
+# Space complexity: O(n^2)
 def reverse(s)
-    raise NotImplementedError, "Method not implemented"
+    if s.length <= 1
+        return s
+    end
+    reverse_s = reverse(s[1..-1])
+    reverse_s += s[0]
+
+    return reverse_s
 end
 
-# Time complexity: ?
-# Space complexity: ?
-def reverse_inplace(s)
-    raise NotImplementedError, "Method not implemented"
+# Time complexity: O(n)
+# Space complexity: O(n)
+def reverse_inplace(s, first = 0, last = s.length-1)
+
+    if s.length == 0 || s.length == 1
+        return s
+    end
+
+    return s if first >= last
+    temp = s[first]
+    s[first] = s[last]
+    s[last] = temp
+
+    return reverse_inplace(s, first + 1, last - 1)
+
 end
 
-# Time complexity: ?
-# Space complexity: ?
+# Time complexity: O(n)
+# Space complexity: O(n)
 def bunny(n)
-    raise NotImplementedError, "Method not implemented"
+    return n if n == 0
+    return 2 + bunny(n - 1)
 end
 
-# Time complexity: ?
-# Space complexity: ?
+# Time complexity: O(n^2)
+# Space complexity: O(n^2)
 def nested(s)
-    raise NotImplementedError, "Method not implemented"
+    return true if s == ""
+    return false if s[0] != "(" || s[-1] != ")"
+    return nested(s[1...-1])
 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.length == 0
+    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"
+# Time complexity: O(n)
+# Space complexity: O(n)
+def is_palindrome(s, first = 0,last = s.length-1)
+
+    return true if s.empty? || first >= last
+    return false if s[first] != s[last]
+
+    return is_palindrome(s, first + 1, last - 1)
+
 end
 
 # Time complexity: ?
 # Space complexity: ?
 def digit_match(n, m)
-    raise NotImplementedError, "Method not implemented"
+    return 1 if n == 0 && m == 0
+    return 0 if n <= 1 || m <= 1
+    if n % 10 == m % 10
+        return 1 + digit_match(n / 10, m / 10)
+    else
+        return digit_match(n / 10, m / 10)
+    end
+end
+
+def fibonacci(n)
+    return 0 if n == 0
+    return 1 if n == 1
+    return fibonacci(n - 1) + fibonacci(n - 2)
 end

test/recursion_writing_test.rb

@@ -167,7 +167,7 @@
   end
 end
 
-xdescribe "nested" do
+describe "nested" do
   it "will return true for empystring" 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