1     class MyQueue<T>
 2     {
 3         Stack<T> stackAppend = new Stack<T>();
 4         Stack<T> stackDelete = new Stack<T>();
 5
 6         public void AppendTail(T value)
 7         {
 8             stackAppend.Push(value);
 9         }
10
11         public T DeleteHead()
12         {
13             if (stackDelete.Count <= 0)
14             {
15                 while (stackAppend.Count > 0)
16                 {
17                     stackDelete.Push(stackAppend.Pop());
18                 }
19             }
20             if (stackDelete.Count <= 0)
21                 throw new Exception("Queue is empty.");
22             return stackDelete.Pop();
23         }
24     }

 1     class MyStack<T>
 2     {
 3         Queue<T> queueA = new Queue<T>();
 4         Queue<T> queueB = new Queue<T>();
 5
 6         public void Push(T value)
 7         {
 8             if (queueA.Count > 0)
 9             {
10                 queueA.Enqueue(value);
11             }
12             else
13             {
14                 queueB.Enqueue(value);
15             }
16         }
17
18         public T Pop()
19         {
20             if (queueA.Count > 0)
21             {
22                 while (queueA.Count > 1)
23                 {
24                     queueB.Enqueue(queueA.Dequeue());
25                 }
26                 return queueA.Dequeue();
27             }
28             else if (queueB.Count > 0)
29             {
30                 while (queueB.Count > 1)
31                 {
32                     queueA.Enqueue(queueB.Dequeue());
33                 }
34                 return queueB.Dequeue();
35             }
36             else
37             {
38                 throw new Exception("Stack is empty.");
39             }
40         }
41     }