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：