feat: add history

app/src/main/java/sudoku/solver/BacktrackingSolver.java

@@ -15,7 +15,7 @@ public class BacktrackingSolver implements Solver {
 	 * @return boolean, valant true si le MultiDoku est résolu, false sinon.
 	 */
 	@Override
-	public boolean solve(MultiDoku doku) {
+	public boolean solve(MultiDoku doku, List<SolverStep> steps) {
 		if (Thread.interrupted())
 			throw new CancellationException("User wants to stop the solver");
 
@@ -34,14 +34,14 @@ public class BacktrackingSolver implements Solver {
 		}
 
 		for (int symbol : possibleSymbols) {
-
 			cellToFill.setSymbolIndex(symbol);
+			addStep(cellToFill, steps);
 			if (this.solve(doku)) {
 				return true;
 			} else {
 				cellToFill.setSymbolIndex(Cell.NOSYMBOL);
+				addStep(cellToFill, steps);
 			}
-
 		}
 		return false;
 	}