Alex - Time

lib/array_intersection.rb

@@ -1,3 +1,11 @@
+# Time Complexity: O(n)
+# Space Complexity: O(n)
+
 def intersection(list1, list2)
-  raise NotImplementedError, "Intersection not implemented"
+  crossroads = []
+
+  list1.each do |n|
+    crossroads << n if list2.include?(n) != false
+  end 
+  return crossroads
 end

lib/palindrome_permutation.rb

@@ -1,4 +1,26 @@
+# Time Complexity: O(n)
+# Space Complexity: O(n)
 
 def palindrome_permutation?(string)
-  raise NotImplementedError, "palindrome_permutation? not implemented"
-end
+  while string.empty? 
+    return true
+  end 
+
+  board = {}
+  letters = string.chars 
+  chalk = 0
+
+  letters.each do |c|
+    board[c] = 0
+  end
+
+  letters.each do |c|
+    if board[c]
+      board[c] += 1
+    end 
+    if board[c] % 2 == 0
+      chalk += 1
+    end
+  end 
+  return chalk == letters.length/2
+end 

lib/permutations.rb

@@ -1,4 +1,23 @@
+# Time Complexity: O(n)
+# Space Complexity: O(n)
 
 def permutations?(string1, string2)
-  raise NotImplementedError, "permutations? not implemented"
+  if string1.length != string2.length 
+    return false
+  end 
+
+  perm = string1.chars
+  mutant = string2.chars 
+  mindflayer = {}
+
+  perm.each do |c|
+    mindflayer[c] = true
+  end 
+
+  mutant.each do |c|
+    if mindflayer[c] != true
+      return false
+    end 
+  end 
+  return true
 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