Elle

lib/max_subarray.rb

@@ -1,8 +1,39 @@
 
-# Time Complexity: ?
-# Space Complexity: ?
+# Time Complexity: O(n) where n is the length of the array
+# Space Complexity: O(1)
+
 def max_sub_array(nums)
-    return 0 if nums == nil
+    return nil if nums == []
+
+    max_so_far = nums[0]
+    sum_ending_here = nums[0]
+
+    # -----------------------------------------------------
+    # SOLUTION 1
+    nums[1..-1].each do |num|
+
+        sum_ending_here = [sum_ending_here + num, num].max
+
+        if max_so_far < sum_ending_here
+            max_so_far = sum_ending_here
+        end
+    end
+
+    # -----------------------------------------------------
+
+    # SOLUTION 2
+
+    # nums[1..-1].each do |num|
+
+    #     sum_ending_here = sum_ending_here + num
+
+    #     if max_so_far < sum_ending_here
+    #         max_so_far = sum_ending_here
+    #     elsif sum_ending_here < 0
+    #         sum_ending_here = 0
+    #     end
+    # end
+    # ----------------------------------------------------- 
 
-    raise NotImplementedError, "Method not implemented yet!"
+    return max_so_far
 end

lib/newman_conway.rb

@@ -1,7 +1,27 @@
+# Time complexity: O(n)
+# Space Complexity: O(n)
 
-
-# Time complexity: ?
-# Space Complexity: ?
 def newman_conway(num)
-  raise NotImplementedError, "newman_conway isn't implemented"
+  solution = [1]
+  raise ArgumentError, "Number must be 1 or greater" if num <1
+  p(num, solution)
+
+  string_solution = ""
+  solution.each do |char|
+    string_solution << "#{char.to_s} "
+  end
+
+  return string_solution[0...-1]
+end
+
+def p(n, s)
+  return s[n-1] if s[n-1]
+
+  if (n == 2) && !s[2-1]
+    s[2-1] = 1
+  else
+    s[n-1] = p(p(n - 1, s), s) + p(n - p(n - 1, s), s)
+  end
+
+  return s[n-1]
 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]
@@ -67,4 +67,28 @@
     expect(answer).must_equal 50
   end
 
+  it "will work for [50, -51, 50]" do
+    # This test (which I added) is failing
+
+    # Arrange
+    input = [50, -51, 50]
+
+    # Act
+    answer = max_sub_array(input)
+
+    # Assert
+    expect(answer).must_equal 50
+  end
+
+  it "will work for [-2,1,-3,4,-1,2,1,-5,4,12]" do
+    # Arrange
+    input = [4,-2,1,-3,4,-1,2,1,-5,4,12]
+
+    # Act
+    answer = max_sub_array(input)
+
+    # Assert
+    expect(answer).must_equal 17
+  end
+
 end