using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Hydro.CommonBase
{
    public class Combine
    {
        public static List<int[]> Get_combine_list(int totalNum, int selectNum)
        {
            _combine_list = new List<int[]>();
            int[] cs = new int[selectNum];
            for (int i = 0; i < selectNum; i++) cs[i] = i;
            _combine_list.Add((int[])cs.Clone());
            Get_combine_inc(totalNum, selectNum, cs, selectNum-1);
            return _combine_list;
        }
        static List<int[]> _combine_list;
        /// <summary>
        /// 
        /// </summary>
        /// <param name="combine_list">组合的集合</param>
        /// <param name="totalNum">所有元素的数量</param>
        /// <param name="selectNum">选取元素的数量</param>
        /// <param name="cs">当前的枚举状态</param>
        /// <param name="k"></param>
        /// <returns></returns>
        private static void Get_combine_inc( int totalNum, int selectNum, int[] cs, int k)
        {
            if(cs[k]< totalNum-1)
            {
                cs[k] += 1;
                for (int i = k + 1; i < selectNum; i++)
                    cs[i] = cs[i - 1] + 1;
                if (k < selectNum - 1) k = selectNum - 1;
                _combine_list.Add((int[])cs.Clone()); 
                Get_combine_inc(totalNum,selectNum,cs,k);


            }
            else if (k>0)
            {
                Get_combine_inc(totalNum, selectNum, cs, k-1);

            }
            else
            {
                return;
            }
            

        }
    }
}