From f85a76957c2e4e8fd96155b8a54041bf19926efc Mon Sep 17 00:00:00 2001 From: Jessica Stone Date: Sun, 11 Oct 2020 20:06:01 -0700 Subject: [PATCH 1/2] implement newman-conway algorithm --- lib/newman_conway.rb | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) diff --git a/lib/newman_conway.rb b/lib/newman_conway.rb index 4c985cd..d773495 100644 --- a/lib/newman_conway.rb +++ b/lib/newman_conway.rb @@ -3,5 +3,14 @@ # Time complexity: ? # Space Complexity: ? def newman_conway(num) - raise NotImplementedError, "newman_conway isn't implemented" -end \ No newline at end of file + raise ArgumentError if num <= 0 + return "1" if num == 1 + return "1 1" if num == 2 + + arr = [0, 1, 1] + while arr.length <= num + arr.push(arr[arr[arr.length - 1]] + arr[arr.length - arr[arr.length - 1]]) + end + + return arr[1..arr.length].join(" ") +end From 1dcf2b1f05c5e44bf291a6d4caf9b869bdca22aa Mon Sep 17 00:00:00 2001 From: Jessica Stone Date: Sat, 17 Oct 2020 15:49:07 -0700 Subject: [PATCH 2/2] implement max_sub_array --- lib/max_subarray.rb | 22 ++++++++++++++++++---- lib/newman_conway.rb | 6 ++---- test/max_sub_array_test.rb | 2 +- 3 files changed, 21 insertions(+), 9 deletions(-) diff --git a/lib/max_subarray.rb b/lib/max_subarray.rb index 5204edb..418d471 100644 --- a/lib/max_subarray.rb +++ b/lib/max_subarray.rb @@ -1,8 +1,22 @@ -# Time Complexity: ? -# Space Complexity: ? +# Time Complexity: O(n), n = length of array +# Space Complexity: O(1) def max_sub_array(nums) - return 0 if nums == nil + return nil if nums.empty? - raise NotImplementedError, "Method not implemented yet!" + max_so_far = nums[0] + max_ending_here = nums[0] + + (1..nums.length-1).each do |i| + max_ending_here = max_ending_here + nums[i] + if(max_ending_here < nums[i]) + max_ending_here = nums[i] + end + + if(max_so_far < max_ending_here) + max_so_far = max_ending_here + end + end + + return max_so_far end diff --git a/lib/newman_conway.rb b/lib/newman_conway.rb index d773495..65e4b0f 100644 --- a/lib/newman_conway.rb +++ b/lib/newman_conway.rb @@ -1,7 +1,5 @@ - - -# Time complexity: ? -# Space Complexity: ? +# Time complexity: O(n), n is num +# Space Complexity: O(1) def newman_conway(num) raise ArgumentError if num <= 0 return "1" if num == 1 diff --git a/test/max_sub_array_test.rb b/test/max_sub_array_test.rb index 3253cdf..e27e1ca 100644 --- a/test/max_sub_array_test.rb +++ b/test/max_sub_array_test.rb @@ -1,6 +1,6 @@ require_relative "test_helper" -xdescribe "max subarray" do +describe "max subarray" do it "will work for [-2,1,-3,4,-1,2,1,-5,4]" do # Arrange input = [-2,1,-3,4,-1,2,1,-5,4]