Ports - Amy M

lib/array_intersection.rb

@@ -1,6 +1,27 @@
 # Returns a new array to that contains elements in the intersection of the two input arrays
-# Time complexity: ?
-# Space complexity: ?
+# Time complexity: O(n+m) where n represents the length the smaller array, and m the larger.
+# Space complexity: O(n), linear, because the additional space required is directly related to
+# length "n" of the smaller array.
 def intersection(array1, array2)
-  raise NotImplementedError
+  if array1 == nil || array2 == nil
+    return []
+  end
+  if array1.length < array2.length
+    larger = array2
+    smaller = array1
+  else
+    larger = array1
+    smaller = array2
+  end
+  my_hash = Hash.new()
+  smaller.each do |num|
+    my_hash[num] = 1
+  end
+  common_elements = []
+  larger.each do |num_1|
+    if my_hash.include? num_1
+      common_elements << num_1
+    end
+  end
+  return common_elements
 end