Java-数据结构与算法-逢3减1-面向对象

1.要求：有一群人围成一圈数数，逢3退1人，要求算出最后留下来的人的下标
2.用面向对象思想，有三个步骤：
(1)有哪些类:找名词--"有一群人围成一圈",所以有类People,PeopleCircle

(2)有哪些属性方法

(3)类的关系

3.代码：

package Test;

public class Count3Quit1$2 {

    public static void main(String[] args) {
        PeopleCircle pc = new PeopleCircle(500);
        int countNum = 0;
        
        People del = pc.getLast(); //先把位置指向last,一开始计数就会指向第一个元素
        while(pc.getCount() > 1){
            countNum++;
            del = del.getRight();//跟踪当前的元素位置，且到了末尾会自动从头开始跟踪
            if(countNum == 3){
                pc.delete(del);
                countNum = 0;
            }
        }
        System.out.println(pc.getCount());
        System.out.println(pc.getFirst());
        System.out.println(pc.getLast());
    }
    
}

//要求：有一群人围成一圈数数，逢3退1人，要求算出最后留下来的人的下标
//用面向对象思想，有三个步骤：
//(1)有哪些类(2)有哪些属性方法(3)类的关系

//(1)有哪些类？找名词--"有一群人围成一圈",所以有类People,PeopleCircle
class People{
    
    private int id;
    private People left;
    private People right;
    
    public People(int id) {
        super();
        this.id = id;
    }

    public People getLeft() {
        return left;
    }

    public void setLeft(People left) {
        this.left = left;
    }

    public People getRight() {
        return right;
    }

    public void setRight(People right) {
        this.right = right;
    }
    
    @Override
    public String toString() {
        return "People-"+id;
    }
}

class PeopleCircle{
    
    private int count = 0;
    
    public int getCount() {
        return count;
    }

    public PeopleCircle(int count) {
        for(int i = 0; i < count ; i++){
            add();
        }
    }

    private People first;
    public People getFirst() {
        return first;
    }

    private People last;
    
    public People getLast() {
        return last;
    }

    public void add(){
        People p = new People(count);
        if(count <= 0 ){
            p.setLeft(p);
            p.setRight(p);
            first = p;
            last = p;
            count++;
        }else {
            last.setRight(p);
            p.setLeft(last);
            p.setRight(first);
            first.setLeft(p);
            last = p;
            count++;
        }
    }
    
    public void delete(People p){
        if(count <= 0){
            System.out.println("已经没有人！");
            return;
        }else if(count == 1){
            first = last = null;
            count--;
        }else{
            p.getLeft().setRight(p.getRight());
            p.getRight().setLeft(p.getLeft());
            
            if(p == first){
                first = p.getRight();
            }else if (p == last){
                last = p.getLeft();
            }
            count--;
        }
    }
}

4.运行结果：