Solve.java

  //TODO
	public boolean search(Sudoku puzzle) {
		puzzle.constraintPropagation();
		if(puzzle.checkContradiction()) return false;
		if(puzzle.checkSolved()) return true;

		//for cell with fewest candidates, loop over candidates
		Cell c = puzzle.getEasiest();
		while(c.numCandidates() > 0) {	
			int candidate = c.getCandidates()[0];
			Sudoku s = (Sudoku) puzzle.clone();
			s.set(c.getRowNum(), c.getColNum(), candidate);
			if(search(s)) {
				puzzle = s;
				System.out.println(s);
				return true;
			}
			else c.remove(candidate);
		}
		return false;
	}