SudokuProblem constructor
SudokuProblem()
Implementation
SudokuProblem() {
var sudoku = Sudoku();
initialState = SudokuState(sudoku.initialBoard);
currentState = SudokuState.fromString(
SudokuProblem.boardToString(SudokuState(sudoku.initialBoard)));
finalState = SudokuState(sudoku.finalBoard);
}