Leaves - Dominique

lib/max_subarray.rb

@@ -1,8 +1,20 @@
 
-# Time Complexity: ?
-# Space Complexity: ?
+# Time Complexity: O(n)
+# Space Complexity: O(1)
 def max_sub_array(nums)
+    # you calculated 
     return 0 if nums == nil
 
-    raise NotImplementedError, "Method not implemented yet!"
+    current_max = nums[0]
+    global_max = nums[0]
+
+    i = 1
+
+    while i < nums.length 
+        current_max = [nums[i], (current_max + nums[i])].max
+        global_max = [global_max, current_max].max
+        i += 1
+    end 
+
+    return global_max
 end

lib/newman_conway.rb

@@ -1,7 +1,41 @@
 
 
-# Time complexity: ?
-# Space Complexity: ?
+# Time complexity: O(n)
+# Space Complexity: O(1)
 def newman_conway(num)
-  raise NotImplementedError, "newman_conway isn't implemented"
-end
+  raise ArgumentError, "num must be >= 0" if num <= 0
+  return "1" if num == 1
+  return "1 1" if num == 2
+
+  # I made a new premade array that was the length plus one of num that was passed in
+  array = Array.new(num + 1){}
+
+  # Build a memo of subproblems
+
+  # value at index 1 and 2 are set two zero, but why is value at index 0 nil? How did everyone initialize
+  # their array?
+  array[1] = 1
+  array[2] = 1
+
+  # initialize i to 3 because values at index 1 and 2 are already set.
+  i = 3
+
+
+  while i < array.length
+
+    # I used the sum of previous values in the array to get the next value. So I initialized i to index  3 since that is the next 
+    # value that needs to be calculated. As a result of plugging 3 into that equation, I got 2. So the value at index 3 is 2. And you'd just keep
+    # doing that until you go past the length of the array. 
+    if i > 2
+      array[i] = array[array[i - 1]] + array[i - array[i - 1]]
+    end
+
+    i += 1
+  end
+
+  # used shift to pop off first value which was nil
+  array.shift()
+
+  # joined them so answer would come out as string instead of array to pass the test
+  return array.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]