CODE-分贓程式的寫法(LINQ進化版)

List<ResultObject> list = ...建立物件清單...;

decimal amtSum = 10000;

decimal weightSum = ...計算權重數字總和...;

foreach (ResultObject o in list)

{

    o.Amount = Math.Round(amtSum * o.Weight / weightSum,

                                0, MidpointRounding.AwayFromZero);

    amtSum -= o.Amount;

    weightSum -= o.Weight;

}

using System;

using System.Collections.Generic;

using System.Linq;

namespace ConsoleApplication1

{

    class Program

    {

        class Share

        {

            public decimal Weight { get; set; }

            public decimal Amount { get; set; }

            public decimal Tax { get; set; }

            public decimal ShippingFee { get; set; }

        }

        static void Main(string[] args)

        {

            //假設有一筆訂單，金額32767, 稅金438, 運費600

            //要依1.2 : 1.5 : 2拆成三份

            //建立三個分配結果物件，設定權重

            List<Share> shares = new List<Share>();

            shares.Add(new Share() { Weight = 1.2M });

            shares.Add(new Share() { Weight = 1.5M });

            shares.Add(new Share() { Weight = 2M });

            //執行分配，參數依序傳入待分配金額，小數位數，權重依據，取回結果

            //其中權重依據及取回結果可使用Lambda表示式

            shares

           .PerfectDivide<Share>(32767, 0, o => o.Weight, (o, v) => o.Amount = v)

           .PerfectDivide<Share>(438, 1, o => o.Weight, (o, v) => o.Tax = v)

       .PerfectDivide<Share>(600, 0, o => o.Weight, (o, v) => o.ShippingFee = v);

            foreach (var share in shares)

                Console.WriteLine("{0:N0}\t{1:N1}\t{2:N0}",

                                  share.Amount, share.Tax, share.ShippingFee);

            Console.Read();

        }

    }

    /// <summary>

    /// 無尾差之完美分贓演算法

    /// </summary>

    public static class PerfectDivider

    {

        /// <summary>

        /// 依提供比例/權重進行無尾差分配計算

        /// </summary>

        /// <param name="weights">權重陣列</param>

        /// <param name="amt">待分配的數量</param>

        /// <param name="decimals">小數位數</param>

        /// <returns>分配結果陣列</returns>

        public static decimal[] Divide(decimal[] weights, decimal amt, int decimals)

        {

            decimal weightSum = weights.Sum(o => o);

            decimal[] result = new decimal[weights.Length];

            for (int i = 0; i < weights.Length; i++)

            {

                result[i] = Math.Round(amt*weights[i]/weightSum, decimals,

                                       MidpointRounding.AwayFromZero);

                amt -= result[i];

                weightSum -= weights[i];

            }

            return result;

        }

        /// <summary>

        /// 以LINQ方式實不同權重之無尾差分配

        /// </summary>

        /// <typeparam name="T">物件型別</typeparam>

        /// <param name="ienum">IEnumerable集合</param>

        /// <param name="amt">待分配量</param>

        /// <param name="decimals">小數位數</param>

        /// <param name="getWeight">回傳權重數字之委派Func&lt;T, decimal&gt;</param>

        /// <param name="resultCallback">傳入分配結果之委派Action&lt;T, decimal&gt;</param>

        /// <returns>繼續傳回IEnumerable</returns>

        public static IEnumerable<T> PerfectDivide<T>(

            this IEnumerable<T> ienum,

            decimal amt, int decimals, Func<T, decimal> getWeight,

            Action<T, decimal> resultCallback)

        {

            decimal[] weights = ienum.Select(getWeight).ToArray();

            decimal[] results = Divide(weights, amt, decimals);

            for (int i = 0; i < results.Length; i++)

                resultCallback(ienum.ElementAt(i), results[i]);

            return ienum;

        }

    }

}