Java抽獎算法第二例

2019-11-26 14:00:48

字體：大中小

來源：轉載

供稿：網友

本文實例為大家分享了java抽獎算法，供大家參考，具體內容如下

1. 算法分析
根據概率將獎品劃分區間，每個區間代表一個獎品，然后抽取隨機數，反查落在那個區間上，即為所抽取的獎品。

2. 代碼
核心算法

public class Arithmetic {  // 放大倍數  private static final int mulriple = 1000000;  public int pay(List<Prize> prizes) {    int lastScope = 0;    // 洗牌，打亂獎品次序    Collections.shuffle(prizes);    Map<Integer, int[]> prizeScopes = new HashMap<Integer, int[]>();    Map<Integer, Integer> prizeQuantity = new HashMap<Integer, Integer>();    for (Prize prize : prizes) {      int prizeId = prize.getPrizeId();      // 劃分區間      int currentScope = lastScope + prize.getProbability().multiply(new BigDecimal(mulriple)).intValue();      prizeScopes.put(prizeId, new int[] { lastScope + 1, currentScope });      prizeQuantity.put(prizeId, prize.getQuantity());      lastScope = currentScope;    }    // 獲取1-1000000之間的一個隨機數    int luckyNumber = new Random().nextInt(mulriple);    int luckyPrizeId = 0;    // 查找隨機數所在的區間    if ((null != prizeScopes) && !prizeScopes.isEmpty()) {      Set<Entry<Integer, int[]>> entrySets = prizeScopes.entrySet();      for (Map.Entry<Integer, int[]> m : entrySets) {        int key = m.getKey();        if (luckyNumber >= m.getValue()[0] && luckyNumber <= m.getValue()[1] && prizeQuantity.get(key) > 0) {          luckyPrizeId = key;          break;        }      }    }    if (luckyPrizeId > 0) {      // 獎品庫存減一    }    return luckyPrizeId;  }}

Prize bean

public class Prize {  /**   * 獎品唯一標示   */  private Integer prizeId;  /**   * 中獎概率   */  private BigDecimal probability;  /**   * 獎品數量   */  private Integer quantity;  public Integer getPrizeId() {    return prizeId;  }  public void setPrizeId(Integer prizeId) {    this.prizeId = prizeId;  }  public BigDecimal getProbability() {    return probability;  }  public void setProbability(BigDecimal probability) {    this.probability = probability;  }  public Integer getQuantity() {    return quantity;  }  public void setQuantity(Integer quantity) {    this.quantity = quantity;  }}

3. 測試

prize1概率: 5%
prize2概率: 10%

prize3概率: 15%
prize4概率: 20%

prize5概率: 50%

public class Test {  public static void main(String[] args) {    List<Prize> prizes = new ArrayList<Prize>();    Prize prize1 = new Prize();    prize1.setPrizeId(1);    prize1.setProbability(new BigDecimal(0.05));    prize1.setQuantity(1);    prizes.add(prize1);    Prize prize2 = new Prize();    prize2.setPrizeId(2);    prize2.setProbability(new BigDecimal(0.10));    prize2.setQuantity(10);    prizes.add(prize2);    Prize prize3 = new Prize();    prize3.setPrizeId(3);    prize3.setProbability(new BigDecimal(0.15));    prize3.setQuantity(20);    prizes.add(prize3);    Prize prize4 = new Prize();    prize4.setPrizeId(4);    prize4.setProbability(new BigDecimal(0.20));    prize4.setQuantity(50);    prizes.add(prize4);    Prize prize5 = new Prize();    prize5.setPrizeId(5);    prize5.setProbability(new BigDecimal(0.50));    prize5.setQuantity(200);    prizes.add(prize5);    int prize1GetTimes = 0;    int prize2GetTimes = 0;    int prize3GetTimes = 0;    int prize4GetTimes = 0;    int prize5GetTimes = 0;    Arithmetic arithmetic = new Arithmetic();    int times = 1000;    for (int i = 0; i < times; i++) {      int prizeId = arithmetic.pay(prizes);      switch (prizeId) {        case 1:          prize1GetTimes++;          break;        case 2:          prize2GetTimes++;          break;        case 3:          prize3GetTimes++;          break;        case 4:          prize4GetTimes++;          break;        case 5:          prize5GetTimes++;          break;      }    }    System.out.println("抽獎次數" + times);    System.out.println("prize1中獎次數" + prize1GetTimes);    System.out.println("prize2中獎次數" + prize2GetTimes);    System.out.println("prize3中獎次數" + prize3GetTimes);    System.out.println("prize4中獎次數" + prize4GetTimes);    System.out.println("prize5中獎次數" + prize5GetTimes);  }}

結果：