老魏帮忙发的木棒问题的最大长度优先匹配原则算法

老魏帮忙发的问题的地址

http://www.cnblogs.com/eastjade/archive/2011/06/22/2086828.html

下面是算法：

定义最木棒的对象

class Item
    {
        public Item(int length, int count)
        {
            Length = length;
            Count = count;
        }

        public int Length { get; set; }

        public int Count { get; set; }
    }

然后定义我们要组装的木棒的长度，这里是21。 定义一个结果类

class Segment
    {
        public Segment()
        {
            Items = new List<int>();
        }

        public List<int> Items { get; set; }

        public int Length
        {
            get { return Items.Sum(); }
        }

        public void RemoveLast()
        {
            Items.RemoveAt(Items.Count - 1);
        }
    }

定义一个MaximumFirstPermutation 类 作为控制类

class MaximumFirstPermutation
    {
        public MaximumFirstPermutation()
        {
            Items = new List<Item>();
        }

        private List<Item> backupItems;

        public List<Item> Items { get; private set; }

        public int SegmentLength { get; set; }


        public Segment[] Segments { get; private set; }


        /// <summary>
        /// 将结果写入文件
        /// </summary>
        /// <param name="fileName"></param>
        public void WriteToFile(string fileName)
        {
            StreamWriter writer = new StreamWriter(fileName);

            List<int> allItems = new List<int>();

            foreach (Segment segment in Segments)
            {
                writer.WriteLine(string.Concat(segment.Items.Select(i => i + " ")));
                allItems.AddRange(segment.Items);
            }


            writer.WriteLine();
            writer.WriteLine("---------------------------");

            foreach (Item backupItem in backupItems)
            {
                Item usedItewm = Items.First(i => i.Length == backupItem.Length);
                writer.WriteLine(string.Format("{0}: total {1}, used {2}, remaining {3}", backupItem.Length, backupItem.Count, allItems.Count(i => i == backupItem.Length), backupItem.Count - allItems.Count(i => i == backupItem.Length)));
            }


            writer.WriteLine();
            writer.WriteLine("---------------------------");

            writer.WriteLine(string.Format("total length: {0}, used {1}, remaining {2}", backupItems.Sum(i => i.Length * i.Count), allItems.Sum(), backupItems.Sum(i => i.Length * i.Count) - allItems.Sum()));


            writer.Close();
        }

        public void Compute()
        {
            backupItems = Items.Select(i => new Item(i.Length, i.Count)).ToList();

            Items = Items.OrderByDescending(i => i.Length).ToList();
            List<Segment> segments = new List<Segment>();

            while (true)
            {

                Segment segment = GetSegment(SegmentLength);

                if (segment != null)
                {
                    segments.Add(segment);
                }
                else
                {
                    break;
                }
            }

            Segments = segments.ToArray();
        }

        /// <summary>
        /// 拼装过程
        /// </summary>
        /// <param name="length"></param>
        /// <returns></returns>
        private Segment GetSegment(int length)
        {
            Segment segment = new Segment();
            Item exact = Items.FirstOrDefault(i => i.Count > 0 && i.Length == length);

            if (exact != null)
            {
                exact.Count--;
                segment.Items.Add(exact.Length);
                return segment;
            }


            foreach (Item item in Items.Where(i => i.Count > 0 && i.Length < length))
            {
                int count = 1;

                while (true)
                {
                    item.Count -= count;

                    for (int i = 1; i <= count; i++)
                    {
                        segment.Items.Add(item.Length);
                    }

                    
                    bool exceeded = segment.Length > length;

                    if (!exceeded)
                    {
                        Segment remainingSegment = GetSegment(length - item.Length);
                        if (remainingSegment != null)
                        {
                            segment.Items.AddRange(remainingSegment.Items);
                            return segment;
                        }
                    }


                    item.Count += count;

                    for (int i = 1; i <= count; i++)
                    {
                        segment.RemoveLast();
                    }


                    if (exceeded)
                    {
                        break;
                    }

                    count++;
                }
            }


            if (segment.Length != length)
            {
                return null;
            }

            return segment;
        }
    }

program.cs main 函数

MaximumFirstPermutation per = new MaximumFirstPermutation() { SegmentLength = 21 };

            per.Items.Add(new Item(1, 100));
            per.Items.Add(new Item(2, 200));
            per.Items.Add(new Item(3, 90));
            per.Items.Add(new Item(4, 14));
            per.Items.Add(new Item(5, 25));
            per.Items.Add(new Item(6, 6));
            per.Items.Add(new Item(7, 20));
            per.Items.Add(new Item(8, 35));
            per.Items.Add(new Item(9, 15));
            per.Items.Add(new Item(10, 21));
            per.Items.Add(new Item(11, 22));
            per.Items.Add(new Item(12, 9));
            per.Items.Add(new Item(13, 16));
            per.Items.Add(new Item(14, 35));
            per.Items.Add(new Item(15, 39));
            per.Items.Add(new Item(16, 41));
            per.Items.Add(new Item(17, 29));
            per.Items.Add(new Item(18, 26));
            per.Items.Add(new Item(19, 18));
            per.Items.Add(new Item(20, 20));
            per.Items.Add(new Item(21, 35));

            per.Compute();
            per.WriteToFile(@"e:\r1.txt");

这个样例数据执行出来之后是

total length: 6479, used 6468, remaining 11

total Segment:48