添加 deque.cs

以 C# 内置的双向队列 LinkedList 为基础，编写了 C# 版本的 deque

codes/csharp/chapter_stack_and_queue/deque.cs

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+/**
+ * File: deque.cs
+ * Created Time: 2022-12-30
+ * Author: moonache (microin1301@outlook.com)
+ */
+
+using NUnit.Framework;
+
+namespace hello_algo.chapter_stack_and_queue
+{
+    public class deque
+    {
+        [Test]
+        public void Test()
+        {
+            /* 初始化双向队列 */
+            LinkedList<int> deque = new LinkedList<int>();
+
+            /* 元素入队 */
+            deque.AddLast(2);   // 添加至队尾
+            deque.AddLast(5);
+            deque.AddLast(4);
+            deque.AddFirst(3);  // 添加至队首
+            deque.AddFirst(1);
+            Console.WriteLine("双向队列 deque = " + String.Join(",", deque.ToArray()));
+
+            /* 访问元素 */
+            int peekFirst = deque.First.Value;  // 队首元素
+            Console.WriteLine("队首元素 peekFirst = " + peekFirst);
+            int peekLast = deque.Last.Value;    // 队尾元素
+            Console.WriteLine("队尾元素 peekLast = " + peekLast);
+
+            /* 元素出队 */
+            deque.RemoveFirst();  // 队首元素出队
+            Console.WriteLine("队首元素出队后 deque = " + String.Join(",", deque.ToArray()));
+            deque.RemoveLast();   // 队尾元素出队
+            Console.WriteLine("队尾元素出队后 deque = " + String.Join(",", deque.ToArray()));
+
+            /* 获取双向队列的长度 */
+            int size = deque.Count;
+            Console.WriteLine("双向队列长度 size = " + size);
+
+            /* 判断双向队列是否为空 */
+            bool isEmpty = deque.Count == 0;
+            Console.WriteLine("双向队列是否为空 = " + isEmpty);
+        }
+    }
+}