54. Spiral Matrix - practice in 2015

Here is my sharing on Leetcode.com.

It is tough job to write a C# solution to go over spiral array to print out all elements in the matrix. I wrote C# solution but I failed multiple test cases, I learned that it is easy to make mistake to count same element twice. Compare to use extra space to mark visit, the solution is prone to the bug for duplicated output.

Also back in 2015, I also need to learn C# better to write more readable code.

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

namespace _54_Spiral_matrix_2015_June
{
    class Program
    {
        static void Main(string[] args)
        {
        }

        /// <summary>
        /// code written in June 12, 2015
        /// </summary>
        /// <param name="matrix"></param>
        /// <returns></returns>
        public IList<int> SpiralOrder(int[,] matrix)
        {
            IList<int> list = new List<int>();

            int len1 = matrix.GetLength(0);
            int len2 = matrix.GetLength(1);

            int[][] matrix_input = new int[len1][];

            for (int i = 0; i < len1; i++)
                matrix_input[i] = new int[len2];

            for (int i = 0; i < len1; i++)
                for (int j = 0; j < len2; j++)
                {
                    matrix_input[i][j] = matrix[i, j];
                }

            ArrayList al = spiralOrder_2(matrix_input);

            foreach (object s in al)
            {
                list.Add((int)s);
            }
            return list;
        }

        public ArrayList spiralOrder_2(int[][] matrix)
        {
            if (matrix == null || matrix.Length == 0 || matrix[0].Length == 0)
                return new ArrayList();
            return spiralOrder_3(matrix, 0, 0, matrix.Length, matrix[0].Length);
        }

        /**
         * Latest update: June 12, 2015 
         * Leetcode: spiral array
         * http://gongxuns.blogspot.ca/2012/12/leetcode-spiral-matrix.html
         * Test case: 
         * 1. empty array 
         * 2. one element:           1 -
         * 2B. one row : 1 2 --
         * 3. one column : 1 |
         *                 2 |
         * 4. more than 1 row, 
         *    or more than 1 column   
         *     1 2
         *     3 4
         *     output: 1 2 4 3 
         * 5. 3 rows, 3 columns
         *    1 2 3
         *    4 5 6
         *    7 8 9
         *    output: 1 2 3 6 9 8 7 4 5 
         * 
         */
        public ArrayList spiralOrder_3(int[][] matrix, int x, int y, int m, int n)
        {
            ArrayList res = new ArrayList();
            // test case: empty array
            if (m <= 0 || n <= 0) return res;

            // test case 2: one row and one column
            if (m == 1 && n == 1)
            {
                res.Add(matrix[x][y]);
                return res;
            }

            //  row, from left to right 
            for (int i = 0; i < n - 1; i++)
            {
                res.Add(matrix[x][y++]);
            }

            //  column, from top to down
            for (int i = 0; i < m - 1; i++)
            {
                res.Add(matrix[x++][y]);
            }

            // conditional: second row, from right to left 
            if (m > 1)
            {
                for (int i = 0; i < n - 1; i++)
                {
                    res.Add(matrix[x][y--]);
                }
            }

            // conditional: second column, from bottom to top
            if (n > 1)
            {
                for (int i = 0; i < m - 1; i++)
                {
                    res.Add(matrix[x--][y]);
                }
            }

            // test case: one row, 1 2 3, where 1 2 is procesed above and 3 is left for next round 
            // one column:
            if (m == 1 || n == 1)
            {
                ArrayList l = spiralOrder_3(matrix, x, y, 1, 1);

                foreach (object val in l)
                    res.Add((int)val);
            }
            else
            {
                ArrayList l = spiralOrder_3(matrix, x + 1, y + 1, m - 2, n - 2);
                foreach (object val in l)
                    res.Add((int)val);
            }

            return res;
        }    
    }
}