Time - Alicia

lib/array_intersection.rb

@@ -1,3 +1,16 @@
 def intersection(list1, list2)
-  raise NotImplementedError, "Intersection not implemented"
+  num_hash = {}
+
+  list1.each do |num|
+    num_hash[num] = 0
+  end
+
+  intersection_array = []
+
+  list2.each do |num|
+    if num_hash.has_key?(num)
+      intersection_array << num
+    end
+  end
+  return intersection_array
 end

lib/palindrome_permutation.rb

@@ -1,4 +1,31 @@
 
 def palindrome_permutation?(string)
-  raise NotImplementedError, "palindrome_permutation? not implemented"
+  return true if string == ""
+
+  char_count_hash = {}
+
+  string.each_char do |char|
+    if char_count_hash.has_key?(char)
+      char_count_hash[char] = char_count_hash[char] + 1
+    else
+      char_count_hash[char] = 1
+    end
+  end
+
+  if (string.length % 2 == 0) #string is even or not?
+    #remove all pairs for which the num of chars is even
+    char_count_hash.reject! { |key, val| (val % 2 == 0) }
+    #if the hash is empty, it passes.
+    return char_count_hash.empty?
+  else
+    #remove all pairs for which the num of chars is even
+    char_count_hash.reject! { |key, val| (val % 2 == 0) }
+    #make sure there's only one pair left
+    if char_count_hash.length == 1
+      #if value is exactly 1, it passes.
+      return char_count_hash.value?(1)
+    else
+      return false
+    end
+  end
 end

lib/permutations.rb

@@ -1,4 +1,30 @@
 
 def permutations?(string1, string2)
-  raise NotImplementedError, "permutations? not implemented"
+  if string1 == "" && string2 == ""
+    return true
+  elsif string1.length != string2.length
+    return false
+  end
+
+  char_count_hash = {}
+
+  string1.each_char do |char|
+    if char_count_hash.has_key?(char)
+      char_count_hash[char] = char_count_hash[char] + 1
+    else
+      char_count_hash[char] = 0
+    end
+  end
+
+  string2.each_char do |char|
+    if char_count_hash.has_key?(char)
+      if char_count_hash[char] == 0
+        char_count_hash.delete(char)
+      else
+        char_count_hash[char] = char_count_hash[char] - 1
+      end
+    end
+  end
+
+  char_count_hash.empty? ? (return true) : (return false)
 end

test/array_intersection_test.rb

@@ -1,6 +1,6 @@
 require_relative "test_helper"
 
-describe "Array Intersection" do
+xdescribe "Array Intersection" do
   it "returns [4] for [2, 3, 4], and [4, 5, 6]" do
     expect(intersection([2, 3, 4], [4, 5, 6])).must_equal [4]
   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

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