用两个栈实现队列

Question

用两个栈来实现一个队列，完成队列的Push和Pop操作。队列中的元素为int类型。

Answer

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package queuebystack;

import java.util.Stack;

public class QueueByStack {

	Stack<Integer> stack1 = new Stack<>();
	Stack<Integer> stack2 = new Stack<>();
		
	private void move(Stack<Integer> source, Stack<Integer> target) {
		while(!source.isEmpty()) {
			target.push(source.pop());
		}
	}
	
	public void enqueue(int node) {
		if(stack1.isEmpty()) {
			move(stack2, stack1);
		}
		stack1.push(node);
	}
	
	public int dequeue() {
		if(stack2.isEmpty()) {
			move(stack1, stack2);
		}
		return stack2.pop();
	}
	
 	
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		QueueByStack obj = new QueueByStack();
        obj.enqueue(1);
        obj.enqueue(2);
        obj.enqueue(3);    
        obj.enqueue(4);
        obj.enqueue(5);
        System.out.println(obj.dequeue());
        System.out.println(obj.dequeue());
        System.out.println(obj.dequeue());
        System.out.println(obj.dequeue());
	}

}