Merge branch 'master' of git.ale-pri.com:Ryuk/Sudoku

app/src/main/java/sudoku/structure/Cell.java

@@ -77,4 +77,10 @@ public class Cell {
 	public boolean isMutable() {
 		return this.isMutable;
 	}
+
+    public int empty() {
+		int oldSymbol = this.symbolIndex;
+		this.symbolIndex = Cell.NOSYMBOL;
+		return oldSymbol;
+    }
 }

app/src/main/java/sudoku/structure/MultiDoku.java

@@ -98,5 +98,21 @@ public class MultiDoku {
 
 		return true;
 	}
+
+	public List<Cell> getFilledCells() {
+		List<Cell> result = new ArrayList<>();
+		for (Cell c : this.getCells()){
+			if (!c.isEmpty()) {
+				result.add(c);
+			}
+		}
+		return result;
+	}
+
+	public void empty(Cell cell) {
+		List<Cell> cells = getCells();
+		Cell cellToEmpty = cells.get(cells.indexOf(cell));
+		cellToEmpty.setSymbolIndex(Cell.NOSYMBOL);
+	}
 }
 

app/src/main/java/sudoku/structure/Sudoku.java

@@ -242,8 +242,9 @@ public class Sudoku {
 		} catch (Exception e) {
 			return result;
 		}
-		for (IConstraint constraint : this.constraints) {
-			if (result.isEmpty()) {
+		for (int i = 0; i < this.constraints.size(); i++) {
+			IConstraint constraint = this.constraints.get(i);
+			if (i == 0) {
 				result.addAll(constraint.getPossibleSymbols(this, cellCoordinates.getX(), cellCoordinates.getY()));
 			} else {
 				result.retainAll(constraint.getPossibleSymbols(this, cellCoordinates.getX(), cellCoordinates.getY()));

app/src/main/java/sudoku/structure/SudokuFactory.java

@@ -4,14 +4,17 @@ import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
 import java.util.Map;
+import java.util.Random;
 
 import sudoku.constraint.BlockConstraint;
 import sudoku.constraint.ColumnConstraint;
 import sudoku.constraint.IConstraint;
 import sudoku.constraint.LineConstraint;
+import sudoku.solver.Solver;
 
 public class SudokuFactory {
 
+	private static final Random random = new Random();
 	public static List<IConstraint> DEFAULT_CONSTRAINTS = Arrays.asList(new BlockConstraint(), new LineConstraint(), new ColumnConstraint());
 
 	private static List<Cell> initCells(int size) {
@@ -66,6 +69,37 @@ public class SudokuFactory {
 		});
 	}
 
+	public static boolean newDokuFromFilledOne (MultiDoku doku, int difficulty) throws Exception {
+
+		if (difficulty > doku.getCells().size()) {
+			throw new Exception();
+		}
+
+		if (difficulty == 0) {
+			return true;
+		}
+
+		List<Cell> cellsThatCanBeEmptied = doku.getFilledCells();
+
+		while (!cellsThatCanBeEmptied.isEmpty()) {
+			int index = random.nextInt(cellsThatCanBeEmptied.size());
+			Cell cellToEmpty = cellsThatCanBeEmptied.get(index);
+
+			int oldSymbol = cellToEmpty.empty();
+
+			if (Solver.countSolution(doku) == 1) {
+				if (newDokuFromFilledOne(doku, --difficulty)) {
+					return true;
+				}
+			}
+
+			cellToEmpty.setSymbolIndex(oldSymbol);
+			cellsThatCanBeEmptied.remove(cellToEmpty);
+		}
+
+		return false;
+    }
+
 	private static Sudoku createRectangleSudoku(int width, int height) {
 		int symbolCount = width * height;
 		List<Cell> cases = initCells(symbolCount);