// Finding a single tour on a "mega" board

//=========================================

// !!! Copy any function you need from file knight1.scala !!!

// !!! or knight2.scala                                   !!! 

//

// If you need any auxiliary function, feel free to 

// implement it, but do not make any changes to the

// templates below.

type Pos = (Int, Int)    // a position on a chessboard 

type Path = List[Pos]    // a path...a list of positions

//(9) Implement a function that searches for a 

//    you have to be careful to write a tail-recursive version as this 

//    function will be called with dimensions of up to 70 * 70

//    and starting field (0, 0). It has to produce a solution within

//    30 seconds.

//def tour_on_mega_board(dim: Int, path: Path) : Option[Path] = ...