whoa

app/src/main/java/sudoku/MutableCell.java

@@ -25,6 +25,11 @@ public class MutableCell extends Cell{
 		setSymboleIndex(NOSYMBOLE);
 	}
 
+	public void clear(int indexSymbol) {
+		hintsSymbolIndex.remove(indexSymbol);
+		this.clear();
+	}
+
 	public List<Integer> getHints() {
 		return this.hintsSymbolIndex;
 	}