diff --git a/lib/recursive-methods.rb b/lib/recursive-methods.rb index fbf6faa..5e74d39 100644 --- a/lib/recursive-methods.rb +++ b/lib/recursive-methods.rb @@ -1,49 +1,100 @@ # Authoring recursive algorithms. Add comments including time and space complexity for each method. +## Don't really understand time and space complexity of recursive functions so I'm leaving that blank for now... will come back! # Time complexity: ? # Space complexity: ? +# referenced online def factorial(n) - raise NotImplementedError, "Method not implemented" + raise ArgumentError if n < 0 + + if n <= 1 + return 1 + else + return n * factorial(n - 1) + end end # Time complexity: ? # Space complexity: ? +# referenced online def reverse(s) - raise NotImplementedError, "Method not implemented" + return s if s.length <= 1 + new_string = reverse(s[1..-1]) + new_string += s[0] + return new_string end # Time complexity: ? # Space complexity: ? +# referenced online def reverse_inplace(s) - raise NotImplementedError, "Method not implemented" + return s if s.length <= 1 + first = s[0] + s = reverse(s[1..-1]) + s += s[0] + return s[0...-1] + first end # Time complexity: ? # Space complexity: ? +# referenced online def bunny(n) - raise NotImplementedError, "Method not implemented" + raise ArgumentError if n < 0 + + return 0 if n == 0 + + return 2 + bunny(n - 1) end # Time complexity: ? # Space complexity: ? +# first one i'm really writing myself w/o internet def nested(s) - raise NotImplementedError, "Method not implemented" + return true if s.length == 0 + return false if s.length % 2 == 1 + + return false unless s[(s.length / 2 - 1)..(s.length / 2)] == "()" + return nested(s[0...s.length / 2 - 1] + s[s.length / 2 + 1..-1]) end # Time complexity: ? # Space complexity: ? +# did this one def search(array, value) - raise NotImplementedError, "Method not implemented" + return false if array.length == 0 + + return true if array.first == value + array.shift + + search(array, value) end # Time complexity: ? # Space complexity: ? +# did this one def is_palindrome(s) - raise NotImplementedError, "Method not implemented" + return true if s.length == 0 + return false if s[0] != s[-1] + + is_palindrome(s[1..-2]) end # Time complexity: ? # Space complexity: ? +# this one works but i got it partly online and am working to understand it def digit_match(n, m) - raise NotImplementedError, "Method not implemented" -end \ No newline at end of file + raise ArgumentError if n < 0 || m < 0 + + if n == 0 && m == 0 + return 1 + else + result = 0 + result += 1 if n % 10 == m % 10 + + if n / 10 == 0 || m / 10 == 0 + return result + end + + return result + digit_match(n / 10, m / 10) + 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