def updateGrid(grid: List[List[Int]], update: List[(Int, Int, Int)]): List[List[Int]] = update match{
        case List() => grid
        case (x,y,z)::xs => updateGrid(grid.updated(x, grid(x).updated(y,z)), update.tail)
      }
      new Sudoku(updateGrid(sudoku.grid, chooseSingleton(allHypothesis)))
    }