package algorithm.queue;
import java.util.Stack;
/**
* 用两个栈来实现一个队列
*
* @param <E>
* @author liuxin
*/
public class QueueWithTwoStacks<E> {
private Stack<E> stack1;
private Stack<E> stack2;
public QueueWithTwoStacks() {
stack1 = new Stack<>();
stack2 = new Stack<>();
}
public boolean isEmpty() {
return stack1.isEmpty() && stack2.isEmpty();
}
public int size() {
return Math.max(stack1.size(), stack2.size());
}
public void enQueue(E item) {
int size = stack2.size();
while (!stack2.isEmpty()) {
stack1.push(stack2.pop());
}
stack2.push(item);
for (int i = 0; i < size; ++i) {
stack2.push(stack1.pop());
}
stack1.push(item);
}
public E deQueue() {
E e = stack2.pop();
int size = stack2.size();
for (int i = 0; i < size; ++i) {
stack2.push(stack1.pop());
}
stack1.pop();
for (int i = 0; i < size; ++i) {
stack1.push(stack2.pop());
}
return e;
}
}