*Algs4-1.3.49栈与队列-(未解决)

 早期版本题目：
1.3.49 Queue with three stacks. Implement a queue with three stacks so that each queue operation takes a constant (worst-case) number of stack operations. Warning :high degree of difficulty

修订后的中文译本题目：
1.3.49栈与队列。用有限个栈实现一个队列，保证每个队列操作(在最坏的情况下)都只需要常数次的栈操作。警告:非常难！

希望聪明人能解。