Leaves - Georgina

lib/max_subarray.rb

@@ -1,8 +1,41 @@
-
-# Time Complexity: ?
-# Space Complexity: ?
+# Time Complexity: O(n)
+# Space Complexity: O(1)
 def max_sub_array(nums)
-    return 0 if nums == nil
-
-    raise NotImplementedError, "Method not implemented yet!"
+  return 0 if nums == nil
+
+  j = 0
+  k = 0
+  while j < nums.length
+    if nums[j] < 0
+      k += 1
+    end
+    j += 1
+  end
+
+  if k == nums.length
+    return nums.max
+  else 
+    return kadane(nums)
+  end
+end 
+
+
+def kadane(nums)
+  return 0 if nums == nil
+
+  max_so_far = 0
+  max_ending_here = 0
+
+  i = 0
+  while i < nums.length
+    max_ending_here = max_ending_here + nums[i]
+    if(max_ending_here < 0)
+      max_ending_here = 0
+    elsif(max_so_far < max_ending_here)
+      max_so_far = max_ending_here
+    end
+    i+=1
+  end
+
+  return max_so_far
 end

lib/newman_conway.rb

@@ -1,7 +1,24 @@
+# Time comPlexity: O(n)
+# Space ComPlexity: O(n)
+def p(n, memo)
+  if memo[n] != nil
+    return memo[n]
+  end
+  if n == 1 || n == 2
+    result = 1
+  else
+    result = p(p(n - 1, memo), memo) + p(n - p(n - 1, memo), memo)
+  end
+  memo[n] = result
+  return result
+end
 
+def newman_conway(n)
+  if n == 0
+    raise ArgumentError
+  end
 
-# Time complexity: ?
-# Space Complexity: ?
-def newman_conway(num)
-  raise NotImplementedError, "newman_conway isn't implemented"
-end
+  memo = [nil,1]
+  p(n, memo)
+  return memo.join(" ").strip!
+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]
@@ -46,14 +46,14 @@
   end
 
   it "will return nil for an empty array" do
-   # Arrange
-   input = []
+  # Arrange
+  input = []
 
-   # Act
-   answer = max_sub_array(input)
+  # Act
+  answer = max_sub_array(input)
 
-   # Assert
-   expect(answer).must_be_nil
+  # Assert
+  expect(answer).must_be_nil
   end
 
   it "will work for [50, -50, 50]" do