Commit 3102164

@@ -0,0 +1,71 @@
+<<-DOC
+Given a singly linked list of integers, determine whether or not it's a palindrome.
+
+Example
+
+For l = [0, 1, 0], the output should be
+isListPalindrome(l) = true;
+For l = [1, 2, 2, 3], the output should be
+isListPalindrome(l) = false.
+Input/Output
+
+[time limit] 4000ms (rb)
+[input] linkedlist.integer l
+
+A singly linked list of integers.
+
+Guaranteed constraints:
+0 ≤ list size ≤ 5 · 10^5,
+-10^9 ≤ element value ≤ 10^9.
+
+[output] boolean
+
+Return true if l is a palindrome, otherwise return false.
+DOC
+
+describe "is_list_palindrome" do
+  def palindrome?(head)
+    true
+  end
+
+  class ListNode
+    attr_accessor :value, :next
+
+    def initialize(value, next_node: nil)
+      @value = value
+      @next = next_node
+    end
+
+    def to_a
+      result = []
+      current = self
+      until current.nil?
+        result.push(current.value)
+        current = current.next
+      end
+      result
+    end
+  end
+
+  def to_list(items)
+    x = nil
+    items.inject(nil) do |memo, item|
+      node = ListNode.new(item)
+      if memo.nil?
+        x = node
+      else
+        memo.next = node
+      end
+      node
+    end
+    x
+  end
+
+  [
+    { l: [0, 1, 0], x: true },
+  ].each do |x|
+    it do
+      expect(palindrome?(to_list(x[:l]))).to eql(x[:x])
+    end
+  end
+end