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：

  1 package Test;
  2
  3 public class Count3Quit1$2 {
  4
  5     public static void main(String[] args) {
  6         PeopleCircle pc = new PeopleCircle(500);
  7         int countNum = 0;
  8
  9         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
 10         while(pc.getCount() > 1){
 11             countNum++;
 12             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
 13             if(countNum == 3){
 14                 pc.delete(del);
 15                 countNum = 0;
 16             }
 17         }
 18         System.out.println(pc.getCount());
 19         System.out.println(pc.getFirst());
 20         System.out.println(pc.getLast());
 21     }
 22
 23 }
 24
 25 //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
 26 //用面向对象思想，有三个步骤：
 27 //(1)有哪些类(2)有哪些属性方法(3)类的关系
 28
 29 //(1)有哪些类？找名词--"有一群人围成一圈",所以有类People,PeopleCircle
 30 class People{
 31
 32     private int id;
 33     private People left;
 34     private People right;
 35
 36     public People(int id) {
 37         super();
 38         this.id = id;
 39     }
 40
 41     public People getLeft() {
 42         return left;
 43     }
 44
 45     public void setLeft(People left) {
 46         this.left = left;
 47     }
 48
 49     public People getRight() {
 50         return right;
 51     }
 52
 53     public void setRight(People right) {
 54         this.right = right;
 55     }
 56
 57     @Override
 58     public String toString() {
 59         return "People-"+id;
 60     }
 61 }
 62
 63 class PeopleCircle{
 64
 65     private int count = 0;
 66
 67     public int getCount() {
 68         return count;
 69     }
 70
 71     public PeopleCircle(int count) {
 72         for(int i = 0; i < count ; i++){
 73             add();
 74         }
 75     }
 76
 77     private People first;
 78     public People getFirst() {
 79         return first;
 80     }
 81
 82     private People last;
 83
 84     public People getLast() {
 85         return last;
 86     }
 87
 88     public void add(){
 89         People p = new People(count);
 90         if(count <= 0 ){
 91             p.setLeft(p);
 92             p.setRight(p);
 93             first = p;
 94             last = p;
 95             count++;
 96         }else {
 97             last.setRight(p);
 98             p.setLeft(last);
 99             p.setRight(first);
100             first.setLeft(p);
101             last = p;
102             count++;
103         }
104     }
105
106     public void delete(People p){
107         if(count <= 0){
108             System.out.println("已经没有人！");
109             return;
110         }else if(count == 1){
111             first = last = null;
112             count--;
113         }else{
114             p.getLeft().setRight(p.getRight());
115             p.getRight().setLeft(p.getLeft());
116
117             if(p == first){
118                 first = p.getRight();
119             }else if (p == last){
120                 last = p.getLeft();
121             }
122             count--;
123         }
124     }
125 }

4.运行结果：