Space - Charlotte

lib/array_intersection.rb

@@ -1,3 +1,19 @@
 def intersection(list1, list2)
-  raise NotImplementedError, "Intersection not implemented"
-end
+  array = []
+  nums = {}
+  i = 0
+
+  while list1.length > i
+    # creating nums hash with number as key and value as true
+    nums[list1[i]] = true
+    i += 1
+  end
+
+  list2.each do |element|
+    # the value at nums[element] is going to be nil or true
+    # check if list2[element] is equal to a key in the nums hash
+    # if it is equal, push element into array b/c that is an intersection. 
+    array << element if nums[element]
+  end
+  array
+end

lib/palindrome_permutation.rb

@@ -1,4 +1,21 @@
 
 def palindrome_permutation?(string)
-  raise NotImplementedError, "palindrome_permutation? not implemented"
-end
+  return true if string.empty?
+
+  # create a new hash which will hold counts of characters
+  # set the default value of all keys to 0
+  letters = Hash.new(0)
+  string.each_char do |char|
+    letters[char] += 1
+  end  
+
+  odd_count = 0
+  # check the hash for characters that appear an odd number of times
+  # the varialbe - key - is not being used thus _key 
+  letters.each do |_key, value|
+    # add to odd character count
+    odd_count += 1 if value.odd?
+  end
+  odd_count <= 1
+
+end

lib/permutations.rb

@@ -1,4 +1,29 @@
-
 def permutations?(string1, string2)
-  raise NotImplementedError, "permutations? not implemented"
-end
+
+  def str_to_hash(string)
+    letters = {}
+    i = 0
+    while string.length > i
+      # check if string[index] is already a key in letters hash
+      if letters.key?(string[i])
+        # if already a key, increment value at said key by 1
+        letters[string[i]] += 1
+      else
+        # if NOT already a key, set the string[index] as a key in letters hash with a value of 1
+        letters[string[i]] = 1
+      end
+      # increment loop 
+      i += 1
+    end
+    letters
+  end
+# call helper method on input strings
+  string1_hash = str_to_hash(string1)
+  string2_hash = str_to_hash(string2)
+#  compare hashes
+  if string1_hash != string2_hash
+    false
+  else
+    true
+  end
+end

test/palindrome_permutation_test.rb

@@ -1,6 +1,6 @@
 require_relative "test_helper"
 
-xdescribe "palindrome_permutation?" do
+describe "palindrome_permutation?" do
   it "will work for hello" do
     expect(palindrome_permutation?("hello")).must_equal false
   end
@@ -19,5 +19,6 @@
 
   it "will return false for raceca" do
     expect(palindrome_permutation?("raceca")).must_equal false
-  end   
-end
+  end 
+
+end

test/permutations_test.rb

@@ -1,6 +1,6 @@
 require_relative "test_helper"
 
-xdescribe "permutations?" do
+describe "permutations?" do
   it "returns true for empty string" do
     expect(permutations?("", "")).must_equal true
   end