Leaves - Alice

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
+    return nil if nums == []
 
-    raise NotImplementedError, "Method not implemented yet!"
+    max_so_far = 0
+    max_ending_here = 0
+    positive_flag = false
+
+    nums.each do |num|
+        if num >= 0
+            positive_flag = true
+        end
+
+        max_so_far = max_so_far + num
+
+        if max_so_far < 0
+            max_so_far = 0
+        end
+
+        if max_so_far > max_ending_here
+            max_ending_here = max_so_far
+        end
+    end
+
+    if !positive_flag
+        largest_num = -Float::INFINITY
+
+        nums.each do |num|
+            if num > largest_num
+                largest_num = num
+            end
+        end
+
+        return largest_num
+    end
+
+    return max_ending_here
 end

lib/newman_conway.rb

@@ -1,7 +1,31 @@
 
 
-# Time complexity: ?
-# Space Complexity: ?
+# Time complexity: O(n)
+# Space Complexity: O(n)
 def newman_conway(num)
-  raise NotImplementedError, "newman_conway isn't implemented"
-end
+  if num == 0
+    raise ArgumentError
+  end
+
+  if num == 1
+    return num.to_s
+  end
+
+  answer = [0, 1, 1]
+
+  (3..num).each do |i|
+    add = answer[answer[i-1]] + answer[i-answer[i-1]]
+    answer << add
+  end
+
+  answer_string = ""
+
+  answer.each do |number|
+    if number != 0
+      answer_string = answer_string + " " + number.to_s
+    end 
+  end
+
+  return answer_string.strip
+
+end

test/max_sub_array_test.rb

@@ -1,70 +1,70 @@
 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]
-
+    
     # Act
     answer = max_sub_array(input)
-
+    
     # Assert
     expect(answer).must_equal 6
   end
-
+  
   it "will work with a totally negative array" do
     # Arrange
     input = [-3, -4, -5, -6, -7]
-
+    
     # Act
     answer = max_sub_array(input)
-
+    
     # Assert
     expect(answer).must_equal(-3)
   end
-
+  
   it "will work with a totally negative array with the largest element at the rear" do
     # Arrange
     input = [ -4, -5, -6, -7, -3]
-
+    
     # Act
     answer = max_sub_array(input)
-
+    
     # Assert
     expect(answer).must_equal(-3)
   end
-
+  
   it "will work with a 1-element array" do
     # Arrange
     input = [3]
-
+    
     # Act
     answer = max_sub_array(input)
-
+    
     # Assert
     expect(answer).must_equal 3
   end
-
+  
   it "will return nil for an empty array" do
-   # Arrange
-   input = []
-
-   # Act
-   answer = max_sub_array(input)
-
-   # Assert
-   expect(answer).must_be_nil
+    # Arrange
+    input = []
+    
+    # Act
+    answer = max_sub_array(input)
+    
+    # Assert
+    expect(answer).must_be_nil
   end
-
+  
   it "will work for [50, -50, 50]" do
     # Arrange
     input = [50, -50, 50]
-
+    
     # Act
     answer = max_sub_array(input)
-
+    
     # Assert
     expect(answer).must_equal 50
   end
-
+  
 end