抽獎算法，抽獎概率算法

抽獎算法，抽獎概率算法

網上找的抽獎代碼都不滿意，自己動手豐衣足食，有需要的可以直接拿去用，不收版權費的。

/// <summary>
/// 抽獎
/// </summary>
public class Prize
{
    /// <summary>
    /// 獎品關鍵字
    /// </summary>
    public string Key { get; set; }

    /// <summary>
    /// 權重/數量
    /// </summary>
    public int Poll { get; set; }


    /// <summary>
    /// 中獎區間
    /// </summary>
    class Area
    {
        /// <summary>
        /// 獎品關鍵字
        /// </summary>
        public string Key { get; set; }

        /// <summary>
        /// 開始索引位置
        /// </summary>
        public int Start { get; set; }

        /// <summary>
        /// 截止索引位置
        /// </summary>
        public int Over { get; set; }
    }

    /// <summary>
    /// 隨機種子
    /// </summary>
    static Random Rand = new Random((int)DateTime.Now.Ticks);


    /// <summary>
    /// 輪盤抽獎，權重值(在輪盤中占的面積大小)為中獎幾率
    /// </summary>
    /// <param name="prizeList">禮品列表（如果不是百分百中獎則輪空需要加入到列表裡面）</param>
    /// <returns></returns>
    public static string Roulette(List<Prize> prizeList)
    {
        if (prizeList == null || prizeList.Count == 0) return string.Empty;
        if (prizeList.Any(x => x.Poll < 1)) throw new ArgumentOutOfRangeException("poll權重值不能小於1");
        if (prizeList.Count == 1) return prizeList[0].Key; //只有一種禮品

        Int32 total = prizeList.Sum(x => x.Poll); //權重和               
        if (total > 1000) throw new ArgumentOutOfRangeException("poll權重和不能大於1000"); //數組存儲空間的限制。最多一千種獎品（及每種獎品的權重值都是1）

        List<int> speed = new List<int>(); //隨機種子
        for (int i = 0; i < total; i++) speed.Add(i);

        int pos = 0;
        Dictionary<int, string> box = new Dictionary<int, string>();
        foreach (Prize p in prizeList)
        {
            for (int c = 0; c < p.Poll; c++) //權重越大所占的面積份數就越多
            {
                pos = Prize.Rand.Next(speed.Count); //取隨機種子坐標
                box[speed[pos]] = p.Key; //亂序 禮品放入索引是speed[pos]的箱子裡面
                speed.RemoveAt(pos); //移除已抽取的箱子索引號
            }
        }
        return box[Prize.Rand.Next(total)];
    }

    /// <summary>
    /// 獎盒抽獎，每個參與者對應一個獎盒，多少人參與就有多少獎盒
    /// </summary>
    /// <param name="prizeList">禮品列表</param>
    /// <param name="peopleCount">參與人數</param>
    /// <returns></returns>
    public static string LunkyBox(List<Prize> prizeList, int peopleCount)
    {
        if (prizeList == null || prizeList.Count == 0) return string.Empty;
        if (prizeList.Any(x => x.Poll < 1)) throw new ArgumentOutOfRangeException("poll禮品數量不能小於1個");
        if (peopleCount < 1) throw new ArgumentOutOfRangeException("參數人數不能小於1人");
        if (prizeList.Count == 1 && peopleCount <= prizeList[0].Poll) return prizeList[0].Key; //只有一種禮品且禮品數量大於等於參與人數

        int pos = 0;
        List<Area> box = new List<Area>();
        foreach (Prize p in prizeList)
        {
            box.Add(new Area() { Key = p.Key, Start = pos, Over = pos + p.Poll }); //把禮品放入獎盒區間
            pos = pos + p.Poll;
        }

        int total = prizeList.Sum(x => x.Poll); //禮品總數
        int speed = Math.Max(total, peopleCount); //取禮品總數和參數總人數中的最大值

        pos = Prize.Rand.Next(speed);
        Area a = box.FirstOrDefault(x => pos >= x.Start && pos < x.Over); //查找索引在獎盒中對應禮品的位置

        return a == null ? string.Empty : a.Key;
    }

}


/*
List<Prize> prizes = new List<Prize>();
prizes.Add(new Prize() { Key = "電腦", Poll = 1 });
prizes.Add(new Prize() { Key = "機櫃", Poll = 2 });
prizes.Add(new Prize() { Key = "鼠標", Poll = 3 });
                        

string lp1 = Prize.LunkyBox(prizes, 6);
Console.WriteLine(lp1);


prizes.Add(new Prize() { Key = "謝謝惠顧", Poll = 5 });
string lp2 = Prize.Roulette(prizes);      
Console.WriteLine(lp2);
*/