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：