Merge pull request 'Fixes #15' (#36) from multiplayer into master

Reviewed-on: #36

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

@@ -126,6 +126,8 @@ public class Cell {
 	}
 
 	public boolean trySetValue(int newValue) {
+		if (!isMutable())
+			return false;
 		if (!canHaveValue(newValue))
 			return false;
 		setSymbolIndex(newValue);

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

@@ -1,6 +1,10 @@
 package sudoku.structure;
 
-import java.util.*;
+import java.util.ArrayList;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Random;
+import java.util.Set;
 
 import sudoku.io.SudokuSerializer;
 
@@ -178,4 +182,18 @@ public class MultiDoku {
 		int randomIndex = rand.nextInt(emptyCells.size());
 		return emptyCells.get(randomIndex);
 	}
+
+	public void clearMutableCells() {
+		for (Sudoku s : getSubGrids()) {
+			for (Cell cell : s.getCells()) {
+				if (cell.isMutable())
+					cell.clearCurrentSymbol();
+			}
+		}
+	}
+
+	public MultiDoku clone() {
+		//TODO: aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaah
+		return SudokuSerializer.deserializeSudoku(SudokuSerializer.serializeSudoku(this));
+	}
 }