Java的击毙囚犯案例

package com.itheima.d1;

import java.util.ArrayList;
import java.util.List;
import java.util.Random;

public class JianYu {
    public static List peoples = new ArrayList<>();

    public static void main(String[] args) {

        Random r = new Random();
        for (int i = 1; i <= 100; i++) {
            while (true) {
                int code = r.nextInt(200) + 1;
                if (isCanUse(code)) {
                    People p = new People(code, i);
                    peoples.add(p);
                    break;
                }
            }
        }
        System.out.println("囚犯站位" + peoples);
            //保留偶数位，等于击毙奇数位
        while (peoples.size() > 1){
            List tempPeoples = new ArrayList<>();
            for (int i = 1; i < peoples.size(); i += 2) {
                People p = peoples.get(i);
                tempPeoples.add(p);
            }
            peoples = tempPeoples;
        }
        People luckPeople = peoples.get(0);
        System.out.println(luckPeople);
    }

    public static boolean isCanUse(int code) {
        for (People people : peoples) {
            if (people.getCode() == code) {
                return false;
            }
        }
        return true;
    }
}

package com.itheima.d1;

public class People {
    private int code;// 编号
    private int location;// 位置

    public People() {
    }

    public People(int code, int location) {
        this.code = code;
        this.location = location;
    }

    public int getCode() {
        return code;
    }

    public void setCode(int code) {
        this.code = code;
    }

    public int getLocation() {
        return location;
    }

    public void setLocation(int location) {
        this.location = location;
    }

    @Override
    public String toString() {
        return "People{" +
                "code=" + code +
                ", location=" + location +
                '}';
    }
}

方法2

package com.itheima.d1;

import java.util.ArrayList;
import java.util.List;
import java.util.Random;

public class Test1 {
    public static void main(String[] args) {
        List peoples = new ArrayList<>();
        Random r = new Random();
        for (int i = 1; i <= 100; i++) {
            int code = r.nextInt(200) + 1;
            if (peoples.contains(code)){
                i--;
            }else {
                peoples.add(code);
            }
        }
        System.out.println(peoples);

        List peoplesBak = new ArrayList<>();
        peoplesBak.addAll(peoples);

        //保留偶数位的到集合里去
         while (peoples.size() > 1){
             for (int i = peoples.size() % 2 == 0 ? peoples.size() - 2 : peoples.size() - 1; i >= 0; i-=2) {
                 peoples.remove(i);
             }
         }

         int code = peoples.get(0);
        System.out.println("幸存者编号" + code);
        int indexOf = peoplesBak.indexOf(code);
        System.out.println("幸存者位置" + (indexOf + 1));
    }
}