feat: add states

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

@@ -68,10 +68,9 @@ public class Solver {
      * @param oldDoku MultiDoku, MultiDoku dont on veut le nombre de solutions.
      * @return int, nombre de solutions possibles.
      */
-    public static int countSolution(MultiDoku oldDoku) {
+    public static int countSolution(MultiDoku doku) {
         int result = 0;
 
-        MultiDoku doku = oldDoku.clone();
 
         if (doku.isSolved()) {
             return 1;
@@ -83,11 +82,12 @@ public class Solver {
         List<Integer> possibleSymbols = cellToFill.getPossibleSymbols();
 
         for (int symbol : possibleSymbols) {
+            doku.getStateManager().pushState();
             cellToFill.setSymbolIndex(symbol);
-            if (Solver.solve(doku) != null) {
+            if (Solver.solve(doku)) {
                 result++;
             }
-            cellToFill.setSymbolIndex(Cell.NOSYMBOL);
+            doku.getStateManager().popState();
         }
 
         return result;
@@ -98,37 +98,35 @@ public class Solver {
      * @param doku MultiDoku, MultiDoku à résoudre.
      * @return boolean, valant true si le MultiDoku est résolu, false sinon.
      */
-    public static MultiDoku solve(MultiDoku oldDoku) {
+    public static boolean solve(MultiDoku doku) {
         if (Thread.interrupted())
             throw new CancellationException("User wants to stop the solver");
 
-        MultiDoku doku = oldDoku.clone();
-
         if (doku.isSolved()) {
-            return doku;
+            return true;
         }
 
         Cell cellToFill = doku.getFirstEmptyCell();
         if (cellToFill == null) {
-            return null;
+            return false;
         }
 
         List<Integer> possibleSymbols = cellToFill.getPossibleSymbols();
         if (possibleSymbols.isEmpty()) {
-            return null;
+            return false;
         }
 
         for (int symbol : possibleSymbols) {
 
             cellToFill.setSymbolIndex(symbol);
-            if (Solver.solve(doku) != null) {
-                return doku;
+            if (Solver.solve(doku)) {
+                return true;
             } else {
                 cellToFill.setSymbolIndex(Cell.NOSYMBOL);
             }
 
         }
-        return null;
+        return false;
     }
 
     /**