using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Text.RegularExpressions;
using System.IO;
using System.Xml;

namespace CSharpTest
{

    class Program
    {
        static void Main(string[] args)
        {
            IEnumerable<int[]> ii = Compute(1, 3, 5, 3);
            foreach (int[] i1 in ii)
            {
                foreach (int i2 in i1)
                    Console.Write(i2);
                Console.WriteLine();
            }


        }

        /// <summary>
        /// 给出sum、min、max和n四个正整数，请输出所有将sum拆分为n个正整数之和，其中每个正整数k都满足：min <= k <= max。这n个正整数之间可以重复，不过由于加法交换率的作用，1 + 2和2 + 1便算是重复的拆分了。
        ///例如，sum = 5，n = 3，min = 1，max = 3，这时候满足条件的拆分方式只有两种：
        /// 1 + 1 + 3 
        /// 1 + 2 + 2
        /// </summary>
        /// <param name="min"></param>
        /// <param name="max"></param>
        /// <param name="sum"></param>
        /// <param name="count">n</param>
        /// <returns></returns>
        public static IEnumerable<int[]> Compute(int min, int max, int sum, int count)
        {
            var list = Enumerable.Range(min, max - min + 1);

            if (count == 1)
                return
                    from item
                        in list
                    where item == sum
                    select new int[] { item };

            return list.SelectMany
                (
                number => Compute(number, max, sum - number, count - 1).Select
                    (
                    item => item.Concat(new int[] { number }).ToArray()
                    )
                );
        }

    }
}