diff --git a/lib/recursive-methods.rb b/lib/recursive-methods.rb index fbf6faa..3b88db8 100644 --- a/lib/recursive-methods.rb +++ b/lib/recursive-methods.rb @@ -1,49 +1,97 @@ # Authoring recursive algorithms. Add comments including time and space complexity for each method. -# Time complexity: ? -# Space complexity: ? +# Time complexity: O(n), where n is the value of the argument passed in (also called 'n'). +# Space complexity: O(n), where n is the value of the argument passed in (also called 'n'). def factorial(n) - raise NotImplementedError, "Method not implemented" + if n == 0 || n == 1 + return 1 + elsif n < 0 + raise ArgumentError, "Please enter a number greater than 0." + else + return n * factorial(n - 1) + end end -# Time complexity: ? -# Space complexity: ? +# Time complexity: O(n), where n is the length of the input string. +# Space complexity: O(n), where n is the length of the input string. def reverse(s) - raise NotImplementedError, "Method not implemented" + if s.length <= 1 + return s + else + return reverse(s[1..-1]) + s[0] + end end -# Time complexity: ? -# Space complexity: ? +# Time complexity: O(n), where n is the length of the input string. +# Space complexity: O(n), where n is the length of the input string. def reverse_inplace(s) - raise NotImplementedError, "Method not implemented" + if s.length <= 1 + return s + else + return s[-1] + reverse(s[1..-2]) + s[0] + end end -# Time complexity: ? -# Space complexity: ? +# Time complexity: O(n), where n is the value of the integer input as n. +# Space complexity: O(n), where n is the value of the integer input as n. 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 end -# Time complexity: ? -# Space complexity: ? +# Time complexity: O(n), where n is the length of the input string. +# Space complexity: O(n), where n is the length of the input string. def nested(s) - raise NotImplementedError, "Method not implemented" + if s == "" + return true + elsif s.length % 2 != 0 + return false + elsif !(s[0] == "(" && s[-1] == ")") + return false + else + return nested(s[1..-2]) + end end -# Time complexity: ? -# Space complexity: ? +# Time complexity: O(n), where n is the length of the array. +# Space complexity: O(n), where n is the length of the array. def search(array, value) - raise NotImplementedError, "Method not implemented" + if array.length == 0 + return false + elsif array[0] == value + return true + else + return search(array[1..-1], value) + end end -# Time complexity: ? -# Space complexity: ? +# Time complexity: O(n) where n is the length of the input string. +# Space complexity: O(n) where n is the length of the input string. def is_palindrome(s) - raise NotImplementedError, "Method not implemented" + if s.length <= 1 + return true + elsif s[0] != s[-1] + return false + else + return is_palindrome(s[1..-2]) + end end -# Time complexity: ? -# Space complexity: ? +# Time complexity: O(n) where n is the number of digits in the input. +# Space complexity: O(n) where n is the number of digits in the input. 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 + if n.length == 0 || m.length == 0 + return 0 + elsif n[-1] == m[-1] + return 1 + digit_match(n[0..-2], m[0..-2]) + else + return digit_match(n[0..-2], m[0..-2]) + end +end diff --git a/specs/recursion_writing_spec.rb b/specs/recursion_writing_spec.rb index d8fb1ed..f2816d0 100644 --- a/specs/recursion_writing_spec.rb +++ b/specs/recursion_writing_spec.rb @@ -1,7 +1,7 @@ -require 'minitest/autorun' -require 'minitest/reporters' +require "minitest/autorun" +require "minitest/reporters" require "minitest/skip_dsl" -require_relative '../lib/recursive-methods' +require_relative "../lib/recursive-methods" describe "factorial" do it "will find the factorial of 0" do @@ -23,8 +23,7 @@ answer = factorial(num) # Assert - expect(answer).must_equal 5*4*3*2*1 - + expect(answer).must_equal 5 * 4 * 3 * 2 * 1 end it "will raise an ArgumentError if given a number not >= 0" do @@ -38,7 +37,7 @@ end end -xdescribe "reverse" do +describe "reverse" do it "will reverse 'cat'" do # Arrange string = "cat" @@ -83,8 +82,7 @@ end end - -xdescribe "reverse_in_place" do +describe "reverse_in_place" do it "will reverse 'cat'" do # Arrange string = "cat" @@ -129,7 +127,7 @@ end end -xdescribe "bunny" do +describe "bunny" do it "returns 0 for 0 bunnies" do # Arrange count = 0 @@ -164,7 +162,7 @@ end end -xdescribe "nested" do +describe "nested" do it "will return true for empystring" do # Arrange string = "" @@ -210,7 +208,7 @@ end end -xdescribe "search" do +describe "search" do it "will return false for empty array" do # Arrange item = "a" @@ -224,43 +222,43 @@ 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 # Arrange item = "x" array = ["b", "c", "a"] - + # Act answer = search(array, item) - + # Assert expect(answer).must_equal false - end - - it "will return true when finding something at the front of the array" do - # Arrange - item = "b" - array = ["b", "c", "a"] - - # Act - answer = search(array, item) - - # Assert - expect(answer).must_equal true - end + end + + it "will return true when finding something at the front of the array" do + # Arrange + item = "b" + array = ["b", "c", "a"] + + # Act + answer = search(array, item) + + # Assert + expect(answer).must_equal true + end end -xdescribe "is_palindrome" do +describe "is_palindrome" do it "will return true for emptystring" do # Arrange string = "" @@ -295,7 +293,7 @@ end end -xdescribe "digit_match" do +describe "digit_match" do it "returns 4 for 1072503891 and 62530841" do # Arrange num1 = 1072503891 @@ -304,8 +302,8 @@ # Act answer = digit_match(num1, num2) - # Assert - expect(answer).must_equal 4 + # Assert + expect(answer).must_equal 4 end it "returns 0 for nonmatching numbers" do @@ -316,8 +314,8 @@ # Act answer = digit_match(num1, num2) - # Assert - expect(answer).must_equal 0 + # Assert + expect(answer).must_equal 0 end it "returns 3 for 841 and 62530841" do @@ -328,7 +326,7 @@ # Act answer = digit_match(num1, num2) - # Assert - expect(answer).must_equal 3 + # Assert + expect(answer).must_equal 3 end -end \ No newline at end of file +end