diff --git a/lib/max_subarray.rb b/lib/max_subarray.rb index 5204edb..be77f20 100644 --- a/lib/max_subarray.rb +++ b/lib/max_subarray.rb @@ -1,8 +1,29 @@ -# Time Complexity: ? -# Space Complexity: ? +# Time Complexity: O(n) - n is the length of the array +# Space Complexity: O(1) - not creating additional space in memory def max_sub_array(nums) - return 0 if nums == nil + return nil if nums.empty? + return nums[0] if nums.length == 1 - raise NotImplementedError, "Method not implemented yet!" -end + total = nums[0] # represents the current sum in question + max = nums[0] # represents the maximum we've seen so far + + i = 1 + while (i < nums.length) + # start comparing: should we take the best we can do, or should we start over from the current number? + if (total + nums[i]) > nums[i] # if current sum plus current number is greater than the current number + total += nums[i] # add it to the sum + if max < total # if the max_so_far is less than the current_total + max = total # max is equal to the total + end + else # the current sum plus the current number is less than or equal to the current number + total = nums[i] # current total equals the current number + if max < nums[i] # if the maximum is less than the current number + max = nums[i] # max is the current number + end + end + i += 1 + end + + return max +end \ No newline at end of file diff --git a/lib/newman_conway.rb b/lib/newman_conway.rb index 4c985cd..e184214 100644 --- a/lib/newman_conway.rb +++ b/lib/newman_conway.rb @@ -1,7 +1,17 @@ - -# Time complexity: ? -# Space Complexity: ? +# Time complexity: O(n) +# Space Complexity: O(n) def newman_conway(num) - raise NotImplementedError, "newman_conway isn't implemented" + raise ArgumentError if num == 0 + return "1" if num == 1 + + arr = [0,1,1] + + i = 3 + while i <= num + arr << arr[arr[i - 1]] + arr[i - arr[i - 1]] + i += 1 + end + + return arr[1..-1].join(' ') end \ No newline at end of file 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]