java数据结构与算法--栈与队列

1、模拟栈

package com.evior.stack;

/**
 * 模拟栈
 */
public class Stack {

    //栈顶指针
    private int top=-1;

    //数组
    private int[] arr;

    public Stack() {
        arr=new int[50];
    }

    public Stack(int maxLength) {
        arr=new int[maxLength];
    }

    //压栈
    public void push(int value){
        //判断栈是否已满
        if (!isFull()){
            top++;
            arr[top]=value;
        }else {
            throw new RuntimeException("栈满，无法入栈");
        }


    }

    //弹栈
    public int pop(){
        if (!isEmpty()){
            top--;
            return arr[top+1];
        }else {
            throw new RuntimeException("栈空，无法弹栈");
        }
    }


    //判空
    public boolean isEmpty(){
        return top==-1;
    }

    //判断栈满
    public boolean isFull(){
        return arr.length-1==top;
    }


}

2、测试

package com.evior.stack;

public class Test {

    public static void main(String[] args) {
        Stack stack=new Stack(3);
        stack.push(1);
        stack.push(2);
        stack.push(3);
        System.out.println(stack.pop());

        while (!stack.isEmpty()){
            System.out.print(stack.pop()+",");
        }

    }
}

3、结果

4、模拟队列

package com.evior.queue;


/**
 * 队列
 */
public class Queue {

    //底层数组
    private long[] arr;

    //有效数据的大小
    private int element;

    //对头
    private int head;

    //队尾
    private int end;


    /**
     * 默认构造器
     */
    public Queue() {
        arr=new long[50];
        element=0;
        head=-1;
        end=-1;
    }

    /**
     * 带参构造
     * @param maxLength
     */
    public Queue(int maxLength) {
       arr=new long[maxLength+1];
        element=0;
        head=-1;
        end=-1;
    }


    /**
     * 入队
     */
    public void insert(long value){
        if (!isFull()){
            //移动数组
            if (element>0){
                for (int i=element-1;i>=0;i--){
                    arr[i+1]=arr[i];
                }
                arr[0]=value;
                element++;
                head++;
            }else {
                arr[++head]=value;
                element++;
            }
        }else {
            throw new RuntimeException("队列已满,无法插入");
        }

    }



    /**
     * 出队
     * @return
     */
    public long out(){
        if (!isEmpty()){
            element--;
            return arr[head--];
        }else {
            throw new RuntimeException("队列为空,无法出队列");
        }

    }

    /**
     * 参看对头
     * @return
     */
    public  long peek(){
        return arr[head];
    }

    /**
     * 判断队是否为空
     */
    public boolean isEmpty(){
        return element==0;
    }

    public boolean isFull(){
        return element==arr.length-1;
    }



}

5、测试

package com.evior.queue;

public class Test {

    public static void main(String[] args) {
        Queue queue=new Queue(5);
        queue.insert(1);
        queue.insert(2);
        while (!queue.isEmpty()){
            System.out.println(queue.out());
        }
        queue.insert(3);
        queue.insert(4);
    }
}

6、结果