Number of path - need to work on the space complexity lower to O(n)

NumberOfPath.cs

using System;

class Solution
{
    public static int NumOfPathsToDest(int n)  // 4
    {
      if( n <= 0) // false 
      {
        return 0; 
      }
      
      var path = new int[n, n]; 
      
      for(int row = 0; row < n; row++ )  // horizontal 
      {
        for(int col = 0; col < n; col++)  // vertical 
        {
          var firstRow = row == 0; 
          if(firstRow)
          {
            path[0, col] = 1; 
          }
          else 
          {
            if(row <= col)
            {
              path[row, col] = path[row - 1, col] + path[row, col - 1]; 
            }
          }
        }
      }
      
      return path[n-1, n-1]; 
    }

    static void Main(string[] args)
    {
      Console.WriteLine(NumOfPathsToDest(4)); 
    }
}

/*
x  x  x  x   14 

x  x  x  5   14     n = 4, output is 5 

x  x  2  5   9 

x   1  2  3   4 

1   1  1  1  1   1    -> go to right, only one way to go to right 

go to first row, 

1  1  1  1   1

and then go to second row

x  1  2  3   4

because it is the sum of left and down - arr[i, j] = arr[i - 1, j] + arr[i, j - 1] if i <= j
*/