diff --git a/lib/recursive-methods.rb b/lib/recursive-methods.rb index fbf6faa..da0ac80 100644 --- a/lib/recursive-methods.rb +++ b/lib/recursive-methods.rb @@ -1,49 +1,92 @@ # 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" + return 1 if n == 0 + raise ArgumentError if n < 0 + + 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 reverse_recursive(s, reversed_string = "", index = -1) +end + +def reverse_recursive(s, reversed_string, index) + return reversed_string if index < -s.length + reversed_string += s[index] + return reverse_recursive(s, reversed_string, index - 1) end -# Time complexity: ? -# Space complexity: ? +# Time complexity: o(n) +# Space complexity: o(n) def reverse_inplace(s) - raise NotImplementedError, "Method not implemented" + return reverse_inplace_recursive(s, last = s.length - 1, index = 0) end -# Time complexity: ? -# Space complexity: ? +def reverse_inplace_recursive(s, last, index) + return s if index >= last + current_letter = s[index] + s[index] = s[last] + s[last] = current_letter + reverse_inplace_recursive(s, last - 1, index + 1) +end + +# Time complexity: o(n) +# Space complexity: o(n) def bunny(n) - raise NotImplementedError, "Method not implemented" + return 0 if n <= 0 + return 2 if n == 1 + return 2 + bunny(n - 1) end -# Time complexity: ? -# Space complexity: ? +# Time complexity: o(n) +# Space complexity: o(n) def nested(s) - raise NotImplementedError, "Method not implemented" + return true if s.empty? + 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 search_recursive(array, value, 0) +end + +def search_recursive(array, value, index) + return false if index > array.length + return true if array[index] == value + + return search_recursive(array, value, index + 1) 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.empty? + return false if s[0] != s[-1] + + return is_palindrome(s[1...-1]) end -# Time complexity: ? -# Space complexity: ? +# Time complexity: o(n) +# Space complexity: o(n) def digit_match(n, m) - raise NotImplementedError, "Method not implemented" -end \ No newline at end of file + if n.digits.length > m.digits.length + return digit_match_recursive(n.digits, m.digits, num_of_pairs = 0, index = 0) + else + return digit_match_recursive(m.digits, n.digits, num_of_pairs = 0, index = 0) + end +end + +def digit_match_recursive(large_num, small_num, num_of_pairs, index) + return num_of_pairs if index == small_num.length + if large_num[index] == small_num[index] + num_of_pairs += 1 + end + return digit_match_recursive(large_num, small_num, num_of_pairs, index + 1) +end diff --git a/test/recursion_writing_test.rb b/test/recursion_writing_test.rb index 820810e..8fc5ba1 100644 --- a/test/recursion_writing_test.rb +++ b/test/recursion_writing_test.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 @@ -328,10 +326,10 @@ # Act answer = digit_match(num1, num2) - # Assert - expect(answer).must_equal 3 + # Assert + expect(answer).must_equal 3 end - + it "returns 1 for (0, 0)" do # Arrange num1 = 0 @@ -340,10 +338,10 @@ # Act answer = digit_match(num1, num2) - # Assert - expect(answer).must_equal 1 + # Assert + expect(answer).must_equal 1 end - + it "returns 1 for (10, 20)" do # Arrange num1 = 10 @@ -352,7 +350,7 @@ # Act answer = digit_match(num1, num2) - # Assert - expect(answer).must_equal 1 + # Assert + expect(answer).must_equal 1 end end