Leetcode 54: Spiral Matrix

Given a matrix of m x n elements (m rows, n columns), return all elements of the matrix in spiral order.

For example,
Given the following matrix:

[
 [ 1, 2, 3 ],
 [ 4, 5, 6 ],
 [ 7, 8, 9 ]
]

You should return [1,2,3,6,9,8,7,4,5].

 

Note: this soluntion beats 100% C# submissions.

public class Solution {
    public IList<int> SpiralOrder(int[,] matrix) {
        int rows = matrix.GetLength(0), cols = matrix.GetLength(1);
        var result = new List<int>();
        
        int upRow = 0, downRow = rows - 1, leftCol = 0, rightCol = cols - 1;
        while (upRow <= downRow && leftCol <= rightCol)
        {
            if (upRow == downRow)
            {
                for (int j = leftCol; j <= rightCol; j++)
                {
                    result.Add(matrix[upRow, j]);
                }
                break;
            }
            
            if (leftCol == rightCol)
            {
                for (int j = upRow; j <= downRow; j++)
                {
                    result.Add(matrix[j, rightCol]);
                }
                break;
            }
            
            for (int j = leftCol; j <= rightCol; j++)
            {
                result.Add(matrix[upRow, j]);
            }
            
            for (int j = upRow + 1; j <= downRow - 1; j++)
            {
                result.Add(matrix[j, rightCol]);
            }
                        
            for (int j = rightCol; j >= leftCol; j--)
            {
                result.Add(matrix[downRow, j]);
            }
            
            for (int j = downRow - 1; j > upRow; j--)
            {
                result.Add(matrix[j, leftCol]);
            }
            
            leftCol++;
            rightCol--;
            upRow++;
            downRow--;
        }
        
        return result;
    }
}