Water - Li

.vscode/launch.json

@@ -0,0 +1,14 @@
+{
+  // Use IntelliSense to learn about possible attributes.
+  // Hover to view descriptions of existing attributes.
+  // For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
+  "version": "0.2.0",
+  "configurations": [
+    {
+      "name": "Debug Local File",
+      "type": "Ruby",
+      "request": "launch",
+      "program": "${workspaceRoot}/main.rb"
+    }
+  ]
+}

lib/max_subarray.rb

@@ -1,8 +1,13 @@
 
-# Time Complexity: ?
-# Space Complexity: ?
+# Time Complexity: O(n) traverse the array
+# Space Complexity: O(1) only integers and 2 elements array are created
 def max_sub_array(nums)
-    return 0 if nums == nil
-
-    raise NotImplementedError, "Method not implemented yet!"
+  return 0 if nums == nil
+  current_sum = 0
+  max_sum = nums[0]
+  nums.each do |num|
+    current_sum = [num, current_sum + num].max
+    max_sum = [max_sum, current_sum].max
+  end
+  return max_sum
 end

lib/newman_conway.rb

@@ -1,7 +1,22 @@
 
 
-# Time complexity: ?
-# Space Complexity: ?
+# Time complexity: O(n) increment i by 1 from 2 to num
+# Space Complexity: O(n) store all the sequences in the array
+# P(n) = P(P(n - 1)) + P(n - P(n - 1))
+# P(3) = P(P(2)) + P(3 - P(2))=1+1
+# p(4) = P(P(3)) + P(4-P(3)) = 1 +1
+
 def newman_conway(num)
-  raise NotImplementedError, "newman_conway isn't implemented"
-end
+  nc_sequence = [1]
+  if num <= 0
+    raise ArgumentError
+  elsif num > 1
+    nc_sequence << 1
+    i = 2 
+    while i < num
+      nc_sequence << nc_sequence[nc_sequence[i - 1] - 1] + nc_sequence[i - nc_sequence[i - 1]]
+      i += 1
+    end
+  end
+  return nc_sequence.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]