全排列和组合算法

C#中使用的全排列和组合算法:

        /// <summary>
        /// 对数组进行组合操作，选取selectCount个元素进行组合
        /// </summary>
        /// <param name="lsArray">即将进行组合操作的数组</param>
        /// <param name="selectCount">选取的元素的个数</param>
        static void Combination(List<string> lsArray, int selectCount)
        {
            int totolcount = lsArray.Count;
            int[] currectselect = new int[selectCount];
            int last = selectCount - 1;
            for (int i = 0; i < selectCount; i++)
            {
                currectselect[i] = i;
            }
            while (true)
            {
                for (int i = 0; i < selectCount; i++)
                {
                    Console.Write(" {0} ", lsArray[currectselect[i]]);
                }
                Console.WriteLine();
                if (currectselect[last] < totolcount - 1)
                {
                    currectselect[last]++;
                }
                else
                {
                    int pos = last;
                    while (pos > 0 && currectselect[pos - 1] == currectselect[pos] - 1)
                    {
                        pos--;
                    }
                    if (pos == 0) return;
                    currectselect[pos - 1]++;
                    for (int i = pos; i < selectCount; i++)
                    {
                        currectselect[i] = currectselect[i - 1] + 1;
                    }
                }
            }
        }

 排列算法(递归):

        /// <summary>
        /// 对数组进行全排列
        /// </summary>
        /// <param name="lsArray">要进行全排列的数组</param>
        /// <param name="begin">进行全排列的开始下标</param>
        /// <param name="end">进行全排列的结束下标</param>
        static void array(List<string> lsArray, int begin, int end)
        {
            if (begin == end)
            {
                for (int i = 0; i <= end; i++)
                    Console.Write(" {0} ", lsArray[i]);
                Console.WriteLine();
            }
            for (int i = begin; i <= end; i++)
            {
                Swap(lsArray, begin, i);
                array(lsArray, begin + 1, end);
                Swap(lsArray, begin, i);
            }
        }

        /// <summary>
        /// 交换数组中的下标为x,y的值
        /// </summary>
        /// <param name="lsArray">该数组</param>
        /// <param name="x"></param>
        /// <param name="y"></param>
        static void Swap(List<string> lsArray, int x, int y)
        {
            string t = lsArray[x];
            lsArray[x] = lsArray[y];
            lsArray[y] = t;
        }