根据总用量计算每种包装规格的购买量和总价

　　

　　最近有这么一个需求，就是给出客户需要的总量，然后根据数据库记录的包装规格，计算出客户需要购买的包装规格种类和个数，而且要保证客户的花费最小。

　　示例图片效果

　　示例代码实现如下。欢迎大家一起讨论。

　　

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Web.Security;
using System.Reflection;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {

            decimal area = 110;
            Console.WriteLine("你的土地面积是：{0}", area);
            decimal amount = 10m;
            Console.WriteLine("你的每亩用量是是：{0}", amount);
            decimal budget = 0;

            decimal budgetMin = 0;

            List<product> products = new List<product>();
            product product1 = new product()
            {
                Id = 1,
                Name = "土豆",
                PkgSpecs = new List<pkgspec>(){
                  new pkgspec() { amount = 202, price = 120, id = 2 },
                  new pkgspec() { amount = 300, price = 40, id = 1 },
                  new pkgspec() { amount = 250, price = 80, id = 3 }}
            };
            product1.PkgSpecs.Sort(new Comparison<pkgspec>(compareAmountDesc));
            products.Add(product1);

            product product2= new product (){ Id=1, Name="白菜", PkgSpecs =new List<pkgspec>(){
                  new pkgspec() { amount = 200, price = 180, id = 2 },
                  new pkgspec() { amount = 100, price = 100, id = 1 },
                  new pkgspec() { amount = 250, price = 250, id = 3 }}};
            product2.PkgSpecs.Sort(new Comparison<pkgspec>(compareAmountDesc));
            products.Add(product2);

            product  product3= new product (){ Id=1, Name="萝卜", PkgSpecs =new List<pkgspec>(){
                  new pkgspec() { amount = 200, price = 210, id = 2 },
                  new pkgspec() { amount = 100, price = 150, id = 1 },
                  new pkgspec() { amount = 250, price = 220, id = 3 }}};
            product3.PkgSpecs.Sort(new Comparison<pkgspec>(compareAmountDesc));
            products.Add(product3);

            //全部商品需要的购买规格和预算
            List<productSelect> proselects = new List<productSelect>();
            //最终选中的商品
            productSelect proselect = null;
            //从一个商品选中的包装
            List<pkgselect> pkgselect = null;
            //总共的用量
            decimal totalAmount = area * amount;
           
            Console.WriteLine("你的总共用量是：{0}", totalAmount);
            //选中的包装个数
            int num = 0;
           
            foreach (product p in products)
            {
                //计算一个商品包装规格及用量
                budget=0;
                totalAmount = area * amount;
                pkgselect = new List<pkgselect>();
                proselect = new productSelect()
                {
                    Id = p.Id,
                    PkgSpecs = new List<pkgselect>(),
                    Budget = budget,
                    Name = p.Name
                };
                                    
                foreach (pkgspec pkg in p.PkgSpecs )
                {
                    if (totalAmount % pkg.amount == totalAmount)
                    {
                        num = 1;
                        budget += num * pkg.price;
                        pkgselect.Add(new pkgselect() { id = pkg.id, num = num, price = pkg.price });
                        break;
                    }
                    else if (totalAmount % pkg.amount == 0)
                    {
                        num = (int)(totalAmount / pkg.amount);
                        budget += num * pkg.price;
                        pkgselect.Add(new pkgselect() { id = pkg.id, num = (int)(totalAmount / pkg.amount), price = pkg.price });
                        break;
                    }
                    else
                    {
                        num = (int)(totalAmount / pkg.amount);
                        budget += num * pkg.price;
                        pkgselect.Add(new pkgselect() { id = pkg.id, num = num, price = pkg.price });
                        totalAmount = totalAmount - num * pkg.amount;
                        continue;
                    }
                }
                proselect.PkgSpecs = pkgselect;
                proselect.Budget = budget;
                proselects.Add(proselect);
            }
            proselects.Sort(compareBudgetAsc);


            foreach (productSelect s in proselects)
            {
                Console.WriteLine("商品 {0} 需要 {1} 个包装规格，总价是 {2}", s.Name, s.PkgSpecs.Count, s.Budget);
            }
            Console.WriteLine("最便宜的是商品 {0} ", proselects[0].Name);

            foreach (pkgselect s in proselects[0].PkgSpecs)
            {
                Console.WriteLine("\t规格 {0} ， 单价 {1}， 需要购买的数量 {2}", s.id, s.price, s.num);
            }
            Console.ReadLine();
        }
        /// <summary>
        /// 从低到高
        /// </summary>
        /// <param name="pkg1"></param>
        /// <param name="pkg2"></param>
        /// <returns></returns>
        private static int compareAmountAsc(pkgspec pkg1, pkgspec pkg2)
        {
            if (pkg1.amount > pkg2.amount)
                return 1;
            if (pkg1.amount < pkg2.amount)
                return -1;
            else
                return 0;
        }
        /// <summary>
        /// 从高到低
        /// </summary>
        /// <param name="pkg1"></param>
        /// <param name="pkg2"></param>
        /// <returns></returns>
        private static int compareAmountDesc(pkgspec pkg1, pkgspec pkg2)
        {
            if (pkg1.amount < pkg2.amount)
                return 1;
            if (pkg1.amount > pkg2.amount)
                return -1;
            else
                return 0;
        }
        /// <summary>
        /// 从低到高
        /// </summary>
        /// <param name="pkg1"></param>
        /// <param name="pkg2"></param>
        /// <returns></returns>
        private static int compareBudgetAsc(productSelect pro1, productSelect pro2)
        {
            if (pro1.Budget > pro2.Budget) return 1;
            if (pro1.Budget < pro2.Budget)
                return -1;
            else
                return 0;
        }
        /// <summary>
        /// 从高到低
        /// </summary>
        /// <param name="pkg1"></param>
        /// <param name="pkg2"></param>
        /// <returns></returns>
        private static int compareBudgetDesc(productSelect pro1, productSelect pro2)
        {
            if (pro1.Budget < pro2.Budget) return 1;
            if (pro1.Budget > pro2.Budget)
                return -1;
            else
                return 0;
        }
    }
    /// <summary>
    /// 选中的包装
    /// </summary>
    class pkgselect
    {
        /// <summary>
        /// 选中ID
        /// </summary>
        public int id;
        /// <summary>
        /// 购买数量
        /// </summary>
        public int num;
        /// <summary>
        /// 单价
        /// </summary>
        public decimal price;
    }
    /// <summary>
    /// 包装类型
    /// </summary>
    class pkgspec : IComparable<pkgspec>
    {
        /// <summary>
        /// 编号
        /// </summary>
        public int id;
        /// <summary>
        /// 包装量
        /// </summary>
        public decimal amount;
        /// <summary>
        /// 价格
        /// </summary>
        public decimal price;

        #region IComparable<pkgspec> Members
        /// <summary>
        /// List<pkgspec>.Sort()默认从低到高
        /// </summary>
        /// <param name="other"></param>
        /// <returns></returns>
        public int CompareTo(pkgspec other)
        {
            if (this.amount > other.amount)
                return 1;
            if (this.amount == other.amount)
                return 0;
            else
                return -1;
        }

        #endregion
    }
    /// <summary>
    /// 代售商品
    /// </summary>
    class product
    {
        /// <summary>
        /// 商品ID
        /// </summary>
        public int Id { set; get; }
        /// <summary>
        /// 商品名称
        /// </summary>
        public string Name { set; get; }
        /// <summary>
        /// 商品包装规格
        /// </summary>
        public List<pkgspec> PkgSpecs { set; get; }
    }
    /// <summary>
    /// 选中的商品
    /// </summary>
     class productSelect : IComparable<productSelect>
    {/// <summary>
        /// 商品ID
        /// </summary>
        public int Id { set; get; }
        /// <summary>
        /// 商品名称
        /// </summary>
        public string Name { set; get; }
        /// <summary>
        /// 需要购买的包装规格
        /// </summary>
        public List<pkgselect> PkgSpecs { set; get; }
        /// <summary>
        /// 总价
        /// </summary>
        public decimal Budget { get; set; }

        #region IComparable<productSelect> Members
         /// <summary>
        /// List<productSelect>.Sort()默认从低到高
         /// </summary>
         /// <param name="other"></param>
         /// <returns></returns>
        public int CompareTo(productSelect other)
        {
            if (this.Budget > other.Budget)
                return 1;
            if (this.Budget < other.Budget)
                return -1;
            else
                return 0;
        }

        #endregion
    }
}