Leetcode 52 - spiralMatrix.cs - pass leetcode online jduge

Leetcode54_spiralMatrix.cs

using System;
using System.Collections.Generic;

class Solution
{    
    /// <summary>
    /// Leetcode 54 
    /// https://leetcode.com/problems/spiral-matrix/#/description
    /// </summary>
    public static void Main()
    { 
        var testcase = new int[1,2]{{1,2}};
        SpiralOrder(testcase); 

    }  

    /// <summary>
    /// Need to test one row, one column
    /// 
    /// </summary>
    /// <param name="matrix"></param>
    /// <returns></returns>
    public static IList<int> SpiralOrder(int[,] matrix)
    {
        int rows = matrix.GetLength(0);
        int cols = matrix.GetLength(1);

        int total = rows * cols;
        var spiral = new int[total];

        int index = 0;

        int leftCol = 0;
        int rightCol = cols - 1;
        int topRow = 0;
        int bottomRow = rows - 1;

        // the idea is to simplify the while loop - one variable checking, check the length of spiral 
        // array intead of compared to the start position of spiral layer. 
        // test cases: one node in the array, one row, one column
        while (index < total)
        {
            // top row - go right, 
            for (int col = leftCol; col <= rightCol; col++)
            {
                var current = matrix[topRow, col];
                spiral[index++] = current;
            }

            // right col - go down
            for (int row = topRow + 1; row <= bottomRow; row++)
            {
                var current = matrix[row, rightCol];
                spiral[index++] = current;
            }

            // go left
            if (bottomRow == topRow)
            {
                continue; 
            }

            for (int col = rightCol - 1; col >= leftCol; col--)
            {
                var current = matrix[bottomRow, col];
                spiral[index++] = current;
            }

            // go up 
            if (leftCol == rightCol)
            {
                continue; 
            }

            for (int row = bottomRow - 1; row > topRow; row--)
            {
                var current = matrix[row, leftCol];
                spiral[index++] = current;
            }

            leftCol++;
            rightCol--;
            topRow++;
            bottomRow--;
        }

        return new List<int>(spiral);
    }
}