A queue of two stacks

【 subject 】

​ Write a class , Queues are implemented with two stacks , Support the basic operation of queue （add、poll、peek）.

【 Ideas 】

​ Prospect knowledge ： Stack , First in, then out ; queue , fifo

​ Two stacks implement queues , Using two stacks is to reverse the data in the stack once , Data such as a Stack , hold a Stack data pop come out push To b Stack , such a Things at the bottom of the stack will arrive b The top of the stack , There are two premises ：

• a Stack to b Stack data , Must take a All data in the stack is pushed into b Stack
• Only b The stack is empty. , To go to b Stack push data

【 Code 】

package keafmd.accumulate.codeinterviewguide.twostacksformaqueue;

import