已知总金额和几个商品单价，查找每个商品各取几个可以最接近或等于总价，取最优解实现程序

100

101

102

103

104

105

106

107

108

109

110

111

112

113

114

115

116

117

118

119

120

121

122

123

124

125

126

127

128

129

130

131

132

133

134

135

136

137

138

139

140

141

142

143

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using System.Xml.Serialization;
 
namespace ConsoleApp1
{
    class Program
    {
        static void Main(string[] args)
        {
            //10个试剂
            var materialList = new List<Material>();
            for (int i = 0; i < 5; i++)
            {
                var material = new Material()
                {
                    Code = i + 1,
                    Name = "Material" + (i + 1).ToString(),
                    Price = (i + 1),
                };
                materialList.Add(material);
                material.QtyList = new List<int>();
                int j = 1;
                //最多取20个
                while (j <= 5)
                {
                    material.QtyList.Add(j);
                    j++;
                }
            }
 
            Console.WriteLine($"MaterialList = {Newtonsoft.Json.JsonConvert.SerializeObject(materialList)}");
            decimal total = 0;
            int totalAmount = 70;
            bool flag = false;
            var diffList = new List<Diff>();
            plus(new Diff(), materialList, diffList, totalAmount, total, ref flag);
            var diff = diffList.OrderBy(p => p.DiffAmt).FirstOrDefault();
            Console.ReadLine();
        } 
         
        public static void plus(Diff diff, List<Material> materialList, List<Diff> diffList, decimal totalAmount, decimal total, ref bool flag)
        {
            if (flag)
                return;
 
            if (materialList != null && materialList.Any())
            {
                var material = materialList.First();
                var list = materialList.Where(p => p.Code != material.Code).ToList();
                foreach (var qty in material.QtyList)
                {
                    if (flag)
                        break;
 
                    if (totalAmount >= material.Price * qty + total)
                    {
                        var oldTotal = total;
                        oldTotal += material.Price * qty;
                        UpdateDiff(diff, material.Code, qty);
                        if (list.Any())
                            plus(diff, list, diffList, totalAmount, oldTotal, ref flag);
                        else
                        {
                            diff.DiffAmt = totalAmount - oldTotal;
                            diffList.Add(DeepCopy(diff));
                            Console.WriteLine(Newtonsoft.Json.JsonConvert.SerializeObject(diff));
                            if (diff.DiffAmt == 0)
                            {
                                flag = true;
                                break;
                            }
                        }
                    }
                }
            }
        }
 
        /// <summary>
        /// 深度拷贝对象
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="obj"></param>
        /// <returns></returns>
        public static T DeepCopy<T>(T obj)
        {
            object retval;
            using (MemoryStream ms = new MemoryStream())
            {
                XmlSerializer xml = new XmlSerializer(typeof(T));
                xml.Serialize(ms, obj);
                ms.Seek(0, SeekOrigin.Begin);
                retval = xml.Deserialize(ms);
                ms.Close();
            }
            return (T)retval;
        }
 
        public static void UpdateDiff(Diff diff, int index, int qty)
        {
            var propName = "Number" + index.ToString();
            if (diff.GetType().GetProperty(propName) != null)
            {
                diff.GetType().GetProperty(propName).SetValue(diff, qty);
            }
        }
 
        public static void showLog(List<int> list)
        {
            string str = string.Join(",", list.ToArray());
            Console.WriteLine(str);
        }
    }
 
    public class Material
    {
        public int Code { get; set; }
        public string Name { get; set; }
        public decimal Price { get; set; }
        public int Qty { get; set; }
        public List<int> QtyList { get; set; }
    }
 
    public class Diff
    {
        public int Number1 { get; set; }
        public int Number2 { get; set; }
        public int Number3 { get; set; }
        public int Number4 { get; set; }
        public int Number5 { get; set; }
        public int Number6 { get; set; }
        public int Number7 { get; set; }
        public int Number8 { get; set; }
        public int Number9 { get; set; }
        public int Number10 { get; set; }
        public decimal DiffAmt { get; set; }
    }
}