feat : logger

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

@@ -1,5 +1,7 @@
 package sudoku.structure;
 
+import sudoku.constraint.IConstraint;
+
 import java.util.ArrayList;
 import java.util.List;
 
@@ -60,12 +62,20 @@ public class MultiDoku {
 	}
 
 	public List<Integer> getPossibleSymbolsOfCell(Cell cellToFill) {
-		for (Sudoku sudoku : this.subGrids) {
-			if (sudoku.contains(cellToFill)) {
-				return sudoku.getPossibleSymbolsOfCell(cellToFill);
-			}
-		}
-		return new ArrayList<>();
+		List<Integer> result = new ArrayList<>();
+		boolean hasBeenFill = false;
+
+        for (Sudoku sudoku : this.subGrids) {
+            if (sudoku.contains(cellToFill)) {
+                if (!hasBeenFill) {
+                    result.addAll(sudoku.getPossibleSymbolsOfCell(cellToFill));
+                    hasBeenFill = true;
+                } else {
+                    result.retainAll(sudoku.getPossibleSymbolsOfCell(cellToFill));
+                }
+            }
+        }
+		return result;
 	}
 
 	public List<Sudoku> getSubGrids() {