Sockets - Kelly

lib/array_intersection.rb

@@ -1,6 +1,26 @@
 # 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 is the number of items of one array and m is the number of items in the other
+# Space complexity: O(n)
 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.length.times do |num|
+    my_hash[smaller[num]] = 1
+  end
+  common_elements = []
+  larger.length.times do |num_1|
+    if my_hash.include? larger[num_1]
+      common_elements << larger[num_1]
+    end
+  end
+  return common_elements
 end