数据结构-队列与栈之间的转换

　　队列：火车过隧道。。。火车头先进隧道先出隧道、、、先进先出

　　栈：桶里倒水再倒出。。。先进后出。。。

两个堆栈实现队列与两个队列实现堆栈

package Test2016.test;

import java.util.LinkedList;
import java.util.Queue;
import java.util.Stack;

public class Test20160329 {

    public static void main(String[] args) {
    
        /**
         * @desc 两个堆栈实现队列
         * @idea 堆栈:先进后出,队列:先进先出
         * */
        MyQueue myQueue = new MyQueue();
        
        System.out.println("入队列顺序:");
        for (int i = 1; i <= 10; i++) {
            System.out.print(i + " ");
            myQueue.push_q(i);
        }
        
        System.out.println("\n用堆栈实现【队列】弹出:");
        for (int i = 0; i < 10; i++) {
            System.out.print(myQueue.pop_q() + " ");
        }
        
        System.out.println("\n######################");
        
        /**
         * @desc 两个队列实现堆栈
         * @idea 堆栈:先进后出,队列:先进先出
         * */
        MyStack myStack = new MyStack();
        
        System.out.println("入堆栈顺序:");
        for (int i = 1; i <= 10; i++) {
            System.out.print(i + " ");
            myStack.push_s(i);
        }
        
        System.out.println("\n用队列实现【堆栈】弹出:");
        for (int i = 0; i < 10; i++) {
            System.out.print(myStack.pop_s() + " ");
        }
        
    }
}

class MyQueue {
    
    private Stack<Integer> s1 = null;
    private Stack<Integer> s2 = null;
    
    public MyQueue() {
        s1 = new Stack<Integer>();
        s2 = new Stack<Integer>();
    }
    
    public Integer push_q(Integer p) {
        s1.push(p);
        return p;
    }
    
    public Integer pop_q() {
        Integer res = null;
        
        if (!s2.isEmpty()) {
            res = s2.pop();
        } else {
            while (!s1.isEmpty()) {
                res = s1.pop();
                s2.push(res);
            }
            
            if (!s2.isEmpty()) {
                res = s2.pop();
            }
        }
        return res;
    }
}


class MyStack {
    
    private Queue<Integer> q1 = null;
    private Queue<Integer> q2 = null;
    
    public MyStack() {
        q1 = new LinkedList<Integer>();
        q2 = new LinkedList<Integer>();
    }
    
    public Integer push_s(Integer p) {
        q1.add(p);
        return p;
    }
    
    public Integer pop_s() {
        Integer res = null;
        boolean flag = true;    //标识变量

        if (q2.size() > 0 && flag == true) {
            flag = false;
            while (q2.size() > 0) {
                if (q2.size() > 0) {
                    res = q2.remove();
                    q1.add(res);
                }
            }
            q1.remove(res);
        } else if (q1.size() > 0 && flag == true) {
            while (q1.size() > 0) {
                if (q1.size() > 0) {
                    res = q1.remove();
                    q2.add(res);
                }
            }
            q2.remove(res);
        }
        
        return res;
    }
}

程序运行输出:

入队列顺序:
1 2 3 4 5 6 7 8 9 10 
用堆栈实现【队列】弹出:
1 2 3 4 5 6 7 8 9 10 
######################
入堆栈顺序:
1 2 3 4 5 6 7 8 9 10 
用队列实现【堆栈】弹出:
10 9 8 7 6 5 4 3 2 1