feat : generation de doku par rapport à une difficulté

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

@@ -4,14 +4,17 @@ import sudoku.constraint.BlockConstraint;
 import sudoku.constraint.ColumnConstraint;
 import sudoku.constraint.IConstraint;
 import sudoku.constraint.LineConstraint;
-import sudoku.structure.*;
+import sudoku.solver.Solver;
 
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Map;
+import java.util.Random;
 
 public class SudokuFactory {
 
+	private static final Random random = new Random();
+
 	private static List<Cell> initCells(int size) {
 		List<Cell> cells = new ArrayList<>(size * size);
 		for (int i = 0; i < size * size; i++) {
@@ -72,4 +75,35 @@ 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;
+    }
 }