Branches - Diana Han

lib/max_subarray.rb

@@ -1,8 +1,23 @@
-
-# Time Complexity: ?
-# Space Complexity: ?
+# Time Complexity: O(n)
+# Space Complexity: O(1)
+# Kadane's Algorithm
 def max_sub_array(nums)
-    return 0 if nums == nil
-
-    raise NotImplementedError, "Method not implemented yet!"
+	return nil if nums.length == 0
+
+	max_so_far = nums[0]
+	max_ending_here = 0
+
+	nums.length.times do |i|
+			max_ending_here = max_ending_here + nums[i]
+
+			if max_so_far < max_ending_here
+					max_so_far = max_ending_here
+			end
+
+			if max_ending_here < 0
+					max_ending_here = 0
+			end
+	end
+
+	return max_so_far
 end

lib/newman_conway.rb

@@ -1,7 +1,18 @@
+# Time complexity: O(n)
+# Space Complexity: O(n)
+def newman_conway(num) # return a string of numbers, in O(n) using memoization
+  raise ArgumentError if num == 0
+  return "1" if num == 1
+  result = "1 1"
+  memo = [0, 1, 1]
 
+  n = 3
+  while n <= num
+    memo[n] = memo[memo[n-1]] + memo[n-memo[n-1]]
+    result += " #{memo[n]}"
 
-# Time complexity: ?
-# Space Complexity: ?
-def newman_conway(num)
-  raise NotImplementedError, "newman_conway isn't implemented"
+    n += 1
+  end
+
+  return result
 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]