From 2c1ef49d93f775d69a884892cefe87fc88ed91c4 Mon Sep 17 00:00:00 2001
From: Pauline Sauget <paulinevsauget@gmail.com>
Date: Sun, 5 May 2019 20:16:08 -0700
Subject: [PATCH] Solve with hash function approach

---
 lib/array_intersection.rb | 24 +++++++++++++++++++++---
 1 file changed, 21 insertions(+), 3 deletions(-)

diff --git a/lib/array_intersection.rb b/lib/array_intersection.rb
index 478b24e..57d7291 100644
--- a/lib/array_intersection.rb
+++ b/lib/array_intersection.rb
@@ -1,6 +1,24 @@
 # Returns a new array to that contains elements in the intersection of the two input arrays
-# Time complexity: ?
-# Space complexity: ?
+# Time complexity: O(n) to hash in, O(m) to look up, where n is length of array1 and m is length of array 2
+# Space complexity: O(n) to add to hash table, O(n) for results array
 def intersection(array1, array2)
-  raise NotImplementedError
+  intersection = []
+  return intersection if !array1 || !array2
+  if array1.length < array2.length
+    smaller = array1
+    larger = array2
+  else
+    smaller = array2
+    larger = array1
+  end
+
+  my_hash = {}
+  smaller.each do |num|
+    my_hash[num] = 1
+  end
+
+  larger.each do |num|
+    intersection << num if my_hash.include?(num)
+  end
+  return intersection
 end