Earth - Christina Minh

lib/max_subarray.rb

@@ -1,8 +1,27 @@
 
-# Time Complexity: ?
-# Space Complexity: ?
+# Time Complexity: O(n)
+# Space Complexity: (1)
 def max_sub_array(nums)
-    return 0 if nums == nil
-
-    raise NotImplementedError, "Method not implemented yet!"
+	return nil if nums.empty?
+
+	max_ending_here = 0
+	# set max so far as first element in case array is totally negative
+	max_so_far = nums[0]
+
+	nums.each do |num|
+		max_ending_here = max_ending_here + num
+
+		# if current element is greater then the max ending here, reset the max ending here as the current element
+		if max_ending_here < num
+			max_ending_here = num
+		end
+
+		# if max ending here is greater than max so far, include the current element in max so far
+		if max_so_far < max_ending_here
+			max_so_far = max_ending_here
+		end
+
+	end
+
+	return max_so_far
 end

lib/newman_conway.rb

@@ -1,7 +1,40 @@
+# [Newman-Conway sequence] is the one which generates the following integer sequence. 1 1 2 2 3 4 4 4 5 6 7 7….. and follows below recursive formula.
 
+# P(1) = 1
+# P(2) = 1
+# for all n > 2
+# P(n) = P(P(n - 1)) + P(n - P(n - 1))
+# Given a number n then print n terms of Newman-Conway Sequence
 
-# Time complexity: ?
-# Space Complexity: ?
+# Examples:
+
+# Input : 13
+# Output : 1 1 2 2 3 4 4 4 5 6 7 7 8
+
+# Input : 20
+# Output : 1 1 2 2 3 4 4 4 5 6 7 7 8 8 8 8 9 10 11 12
+
+# Time complexity: O(n)
+# Space Complexity: O(n)
 def newman_conway(num)
-  raise NotImplementedError, "newman_conway isn't implemented"
-end
+	raise ArgumentError, "Number must be greater than 0" if num <= 0
+  return "1" if num == 1
+
+	p = []
+
+	n = 1
+	while n <= num
+		if n <= 2
+			p.append(1)
+		else
+			# P(n) = P(P(n - 1)) + P(n - P(n - 1))
+			# minus 1 to address 0 indexing
+			p.append(p[p[n - 2] - 1] + p[n - p[n - 2] - 1])		
+		end
+
+		n += 1
+	end
+
+	return p.join(" ")
+
+end

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]