Algorithms

Kyudos wrote:

I think throwing the points at a Travelling Salesman algorithm might be less complicated.

public static System.Collections.Generic.IEnumerable<System.Collections.Generic.IList<int>>
nQueens
(
  int HowMany
)
{
  int[] board = new int [ HowMany ] ;
  int   row   = 0 ;

  board [ row ] = -1 ;

  while ( row >= 0 )
  {
    board [ row ]++ ;

    if ( board [ row ] == HowMany )
    {
      row-- ;
    }
    else
    {
      int i ;

      for ( i = 0 ; i < row ; i++ )
      {
        int diff = board [ row ] - board [ i ] ;

        if ( ( diff == 0 ) || ( System.Math.Abs ( diff ) == ( row - i ) ) )
        {
          break ;
        }
      }

      if ( i == row )
      {
        row++ ;

        if ( row == HowMany )
        {
          yield return ( System.Array.AsReadOnly ( board ) ) ;

          row-- ;
        }
        else
        {
          board [ row ] = -1 ;
        }
      }
    }
  }

  yield break ;
}

C:\Projects>nQueens 438330000
^C
C:\Projects>nQueens 438335000
System.OutOfMemoryException: Exception of type 'System.OutOfMemoryException' was thrown.
   at PIEBALD.Lib.LibMth.<nQueens>d__0.MoveNext()
   at PIEBALD.Utilities.nQueens.Main(String[] args)

Member 4194593 wrote:

Desert Rat from West Phoenix