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.

1 public class Solution { 2     public IList
     
       SpiralOrder(int[,] matrix) { 3         int rows = matrix.GetLength(0), cols = matrix.GetLength(1); 4         var result = new List
      
       (); 5          6         int upRow = 0, downRow = rows - 1, leftCol = 0, rightCol = cols - 1; 7         while (upRow <= downRow && leftCol <= rightCol) 8         { 9             if (upRow == downRow)10             {11                 for (int j = leftCol; j <= rightCol; j++)12                 {13                     result.Add(matrix[upRow, j]);14                 }15                 break;16             }17             18             if (leftCol == rightCol)19             {20                 for (int j = upRow; j <= downRow; j++)21                 {22                     result.Add(matrix[j, rightCol]);23                 }24                 break;25             }26             27             for (int j = leftCol; j <= rightCol; j++)28             {29                 result.Add(matrix[upRow, j]);30             }31             32             for (int j = upRow + 1; j <= downRow - 1; j++)33             {34                 result.Add(matrix[j, rightCol]);35             }36                         37             for (int j = rightCol; j >= leftCol; j--)38             {39                 result.Add(matrix[downRow, j]);40             }41             42             for (int j = downRow - 1; j > upRow; j--)43             {44                 result.Add(matrix[j, leftCol]);45             }46             47             leftCol++;48             rightCol--;49             upRow++;50             downRow--;51         }52         53         return result;54     }55 }