01.程序结构划分

02.去零

有序向量“唯一化”的思路。

        /// <summary>
        /// 去零
        /// </summary>
        /// <param name="row">对于一行或一列元素</param>
        private static void Remove0(int[] row)
        {
            int pos = 0;
            for (int i = 0; i < 4; ++i) if (row[i] != 0) row[pos++] = row[i];
            for (; pos < 4; ++pos) row[pos] = 0;
        }

03.合并

        /// <summary>
        /// 合并
        /// </summary>
        /// <param name="row">对于一行或一列元素，完成一次向左合并的操作</param>
        private static void Merge(int[] row)
        {
            // 去零
            Remove0(row);

            // 相邻相同则合并
            for (int i=0; i<4-1; ++i)
            {
                if (row[i] != 0 && row[i] == row[i+1])
                {
                    row[i] *= 2;
                    row[i + 1] = 0;
                }
            }
            // 去零
            Remove0(row);
        }

04.上移

        /// <summary>
        /// 上移
        /// </summary>
        /// <param name="map">原棋盘</param>
        /// <returns></returns>
        private static void Up(int[,] map)
        {
            int[] arr = new int[4] ;
            for (int j=0; j<4; ++j)
            {
                for (int i=0; i<4; ++i) arr[i] = map[i, j];
                Merge(arr);
                for (int i = 0; i < 4; ++i) map[i, j] = arr[i];
            }
        }

05.下移/左移/右移，只是取数据的方向不同

比如，“下移” 取数据和还数据的方向与“上移”相反。

        /// <summary>
        /// 下移
        /// </summary>
        /// <param name="map">原棋盘</param>
        /// <returns></returns>
        private static int[,] Down(int[,] map)
        {
            int[] arr = new int[4];
            for (int j = 0; j < 4; ++j)
            {
                for (int i = 0; i < 4; ++i) arr[3-i] = map[i, j];
                Merge(arr);
                for (int i = 0; i < 4; ++i) map[i, j] = arr[3-i];
            }
            return map;
        }

        /// <summary>
        /// 左移
        /// </summary>
        /// <param name="map"></param>
        /// <returns></returns>
        private static int[,] Left(int[,] map)
        {
            int[] arr = new int[4];
            for (int i = 0; i < 4; ++i)
            {
                for (int j = 0; j < 4; ++j) arr[j] = map[i, j];
                Merge(arr);
                for (int j = 0; j < 4; ++j) map[i, j] = arr[j];
            }
            return map;
        }

        /// <summary>
        /// 右移
        /// </summary>
        /// <param name="map">原棋盘</param>
        /// <returns></returns>
        private static int[,] Right(int[,] map)
        {
            int[] arr = new int[4];
            for (int i = 0; i < 4; ++i)
            {
                for (int j = 0; j < 4; ++j) arr[3-j] = map[i, j];
                Merge(arr);
                for (int j = 0; j < 4; ++j) map[i, j] = arr[3-j];
            }
            return map;
        }

06.提高可读性

枚举
enum Direction { up, down, left, right }

        /// <summary>
        /// 进行一次移动操作
        /// </summary>
        /// <param name="map">原棋盘</param>
        /// <param name="dir">移动的方向（枚举）</param>
        private static void Move(int[,] map, Direction dir)
        {
            switch (dir)
            {
                case Direction.up:
                    Up(map); break;
                case Direction.down:
                    Down(map); break;
                case Direction.left:
                    Left(map); break;
                case Direction.right:
                    Right(map); break;
            }
        }