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

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);