Space - Jessica

lib/array_intersection.rb

@@ -1,3 +1,27 @@
+# Time complexity: O(n^2)
+# Space complexity: O(n)
+
 def intersection(list1, list2)
-  raise NotImplementedError, "Intersection not implemented"
+  hash = {}
+  list1.each do |i|
+    if hash[i/10]
+      hash[i/10] << i
+    else
+      hash[i/10] = [i]
+    end
+  end
+
+  array = []
+  list2.each do |i|
+    if hash[i/10]
+      hash[i/10].each do |x|
+        if i == x
+          array << i
+          break
+        end
+      end
+    end
+  end
+
+  return array
 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"
+  hash = {}
+
+  string.length.times do |i|
+    if hash[string[i]]
+      hash[string[i]] += 1
+    else
+      hash[string[i]] = 1
+    end
+  end
+
+
+  odd = 0
+  hash.each do |k, v|
+    if v % 2 != 0
+      if v == 1
+        return false if (odd += 1) > 1
+      end
+    end
+  end
+
+  return true
 end

lib/permutations.rb

@@ -1,4 +1,24 @@
-
+# Time complexity: O(n)
+# Space complexity: O(n)
 def permutations?(string1, string2)
-  raise NotImplementedError, "permutations? not implemented"
+  return false if string1.length != string2.length
+
+  hash = {}
+  string1.length.times do |i|
+    if hash[string1[i]]
+      hash[string1[i]] += 1
+    else
+      hash[string1[i]] = 1
+    end
+  end
+
+  string2.length.times do |i|
+    if hash[string2[i]] && hash[string2[i]] > 0
+      hash[string2[i]] -= 1
+    else
+      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