diff --git a/lib/recursive-methods.rb b/lib/recursive-methods.rb index fbf6faa..2d59b3d 100644 --- a/lib/recursive-methods.rb +++ b/lib/recursive-methods.rb @@ -1,49 +1,87 @@ +require 'pry' # 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" + raise ArgumentError.new("BAD") if n < 0 + return 1 if n == 0 + return n if n == 1 + return n * factorial(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 + return reverse(s[1..-1]) + s[0] 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, i = 0) + return s if i == s.length / 2 + s[i], s[s.length - i - 1] = s[s.length - i - 1], s[i] + s = reverse_inplace(s, i += 1) 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) end -# Time complexity: ? -# Space complexity: ? +# Time complexity: O(n^2) since using .length? +# Space complexity: O(n) def nested(s) - raise NotImplementedError, "Method not implemented" + return false if s.length % 2 != 0 + return true if s == "" + return true if s == "()" + center_l = s.length / 2 - 1 + center_r = center_l + 1 + if s[center_l] + s[center_r] != "()" + return false + else + next_string = s[center_l - 1] + s[center_r + 1] + end + return nested(next_string) 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 + new_array = array[1..-1] + 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.length <= 1 + if s[0] != s[-1] + return false + else + next_string = s[1..-2] + end + return is_palindrome(next_string) end -# Time complexity: ? -# Space complexity: ? +# Time complexity: O(n^2) since it uses .length in each loop? +# Space complexity: O(n) def digit_match(n, m) - raise NotImplementedError, "Method not implemented" -end \ No newline at end of file + n = n.to_s + m = m.to_s + return 0 if n == nil || m == nil || n.length == 0 || m.length == 0 + match = n[-1] == m[-1] + if match && (n.length == 1 || m.length == 1) + return 1 + elsif !match && (n.length == 1 || m.length == 1) + return 0 + elsif !match + return 0 + digit_match(n[0..-2].to_i, m[0..-2].to_i) + else + return 1 + digit_match(n[0..-2].to_i, m[0..-2].to_i) + end +end diff --git a/test/recursion_writing_test.rb b/test/recursion_writing_test.rb index 820810e..b19c650 100644 --- a/test/recursion_writing_test.rb +++ b/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" @@ -224,15 +224,15 @@ end it "will return true when looking for something in the array" do - # Arrange - item = "a" - array = ["b", "c", "a"] + # Arrange + item = "a" + array = ["b", "c", "a"] - # Act - answer = search(array, item) + # Act + answer = search(array, item) - # Assert - expect(answer).must_equal true + # Assert + expect(answer).must_equal true end it "will return false when looking for something not in the array" do @@ -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