2 and 3 Strong links (Groupd)

Improved both TurbotFish.java and ThreestrongLinks.java to accommodate Grouped strong links including ER and Line Grouped strong links. There is also the Grouped strong link in a box that is not ER as well. Clunky and may need some efiiciency related revision at some stage. some modifications to Grid.java to help in search for EmA in block/line constraints

diuf/sudoku/Grid.java

@@ -802,52 +802,118 @@ public static abstract class Region {
     	public abstract int getRegionTypeIndex();
     	public abstract int getRegionIndex();
 
+		//4 Cell set corresponds to cells in block that share exactly 2 columns and 2 rowes
+		private static int[][]  blocksEmptyCells = new int[][] {
+			{4, 5, 7, 8},
+			{3, 5, 6, 8},
+			{3, 4, 6, 7},
+			{1, 2, 7, 8},
+			{0, 2, 6, 8},
+			{0, 1, 6, 7},
+			{1, 2, 4, 5},
+			{0, 2, 3, 5},
+			{0, 1, 3, 4},
+			{6, 7, 8, -1},
+			{3, 4, 5, -1},
+			{0, 1, 2, -1},
+			{2, 5, 8, -1},
+			{1, 4, 7, -1},
+			{0, 3, 6, -1}
+		};
+		//4 Cell set corresponds to cells in block that share exactly 1 column and 1 row or 2 lines 
+		//without the cell at the intersection
+		private static int[][]  blockGroupedCells = new int[][] {
+			{3, 6, -1, 1, 2, -1},
+			{4, 7, -1, 0, 2, -1},
+			{5, 8, -1, 0, 1, -1},
+			{0, 6, -1, 4, 5, -1},
+			{1, 7, -1, 3, 5, -1},
+			{2, 8, -1, 3, 4, -1},
+			{0, 3, -1, 7, 8, -1},
+			{1, 4, -1, 6, 8, -1},
+			{2, 5, -1, 6, 7, -1},
+			{0, 1, 2, 3, 4, 5},
+			{0, 1, 2, 6, 7, 8},
+			{3, 4, 5, 6, 7, 8},
+			{0, 3, 6, 1, 4, 7},
+			{0, 3, 6, 2, 5, 8},
+			{1, 4, 7, 2, 5, 8}
+		};
+		private static int[][]  LineEmptyCells = new int[][] {
+			{0,1,2},
+			{3,4,5},
+			{6,7,8},
+		};			
+		private static int[][]  LineGroupedCells = new int[][] {
+			{3,4,5,6,7,8},
+			{0,1,2,6,7,8},
+			{0,1,2,3,4,5}
+		};			
 		//4 Cell set corresponds to cells in block that share exactly 2 columns and 2 rowes
 		public BitSet Rectangle(int index) {
-        	BitSet blockRectangleCellSet = new BitSet(9);
-            int[][]  blocksRectangleCells = new int[][] {
-				{4, 5, 7, 8},
-				{3, 5, 6, 8},
-				{3, 4, 6, 7},
-				{1, 2, 7, 8},
-				{0, 2, 6, 8},
-				{0, 1, 6, 7},
-				{1, 2, 4, 5},
-				{0, 2, 3, 5},
-				{0, 1, 3, 4}
-			};
-			for(int i = 0; i < 4; i++) {
-				blockRectangleCellSet.set(blocksRectangleCells[index][i]);
-			}
-			return blockRectangleCellSet;
+        	BitSet blockEmptyCellSet = new BitSet(10);
+			for(int i = 0; i < 4; i++)
+				if (blocksEmptyCells[index][i] >= 0)
+					blockEmptyCellSet.set(blocksEmptyCells[index][i]);
+			return blockEmptyCellSet;
 		}
 
 		//4 Cell set corresponds to cells in block that share exactly 1 column and 1 row 
 		//without the cell at the intersection
 		public BitSet Cross(int index) {
-        	BitSet blockCrossCellSet = new BitSet(9);
-            int[][]  blocksCrossCells = new int[][] {
-				{3, 6, 1, 2},
-				{4, 7, 0, 2},
-				{5, 8, 0, 1},
-				{0, 6, 4, 5},
-				{1, 7, 3, 5},
-				{2, 8, 3, 4},
-				{0, 3, 7, 8},
-				{1, 4, 6, 8},
-				{2, 5, 6, 7}
-			};
-			for(int i = 0; i < 4; i++) {
-				blockCrossCellSet.set(blocksCrossCells[index][i]);
-			}
-			return blockCrossCellSet;
+        	BitSet blockGroupedCellSet = new BitSet(10);
+			for(int i = 0; i < 6; i++)
+				 if (blockGroupedCells[index][i] >= 0)
+					blockGroupedCellSet.set(blockGroupedCells[index][i]);
+			return blockGroupedCellSet;
+		}
+
+		//2 Cell set corresponds to cells in block Cross cells that share 1 row 
+		//without the cell at the intersection
+		public BitSet crossBlade1(int index) {
+        	BitSet blockGroupedCellSet = new BitSet(10);
+			for(int i = 0; i < 3; i++)
+				if (blockGroupedCells[index][i] >= 0)
+					blockGroupedCellSet.set(blockGroupedCells[index][i]);
+			return blockGroupedCellSet;
+		}
+
+		//2 Cell set corresponds to cells in block Cross cells that share 1 column 
+		//without the cell at the intersection
+		public BitSet crossBlade2(int index) {
+        	BitSet blockGroupedCellSet = new BitSet(10);
+			for(int i = 3; i < 6; i++)
+				if (blockGroupedCells[index][i] >= 0)
+					blockGroupedCellSet.set(blockGroupedCells[index][i]);
+			return blockGroupedCellSet;
 		}
 
 		//cellIndex of blockCell at centre of Cross Cell set 
 		public int Heart(int index) {
 			int[] blocksHeartCells = new int[] {0, 1, 2, 3, 4, 5, 6, 7, 8};
 			return blocksHeartCells[index];
 		}
+
+		public BitSet lineEmptyCells(int index) {
+			BitSet lineEmptyCellSet = new BitSet(10);
+			for(int i = 0; i < 3; i++) 
+				lineEmptyCellSet.set(LineEmptyCells[index][i]);
+			return lineEmptyCellSet;
+		}
+
+		public BitSet lineBlade1(int index) {
+        	BitSet lineBladeCellSet = new BitSet(10);
+			for(int i = 0; i < 3; i++)
+				lineBladeCellSet.set(LineGroupedCells[index][i]);
+			return lineBladeCellSet;
+		}
+
+		public BitSet lineBlade2(int index) {
+        	BitSet lineBladeCellSet = new BitSet(10);
+			for(int i = 0; i < 3; i++)
+				lineBladeCellSet.set(LineGroupedCells[index][i+3]);
+			return lineBladeCellSet;
+		}
 
 		/**
          * Get a cell of this region by index. The order in which cells are

diuf/sudoku/Settings.java

@@ -17,9 +17,9 @@
 public class Settings {
 
     public final static int VERSION = 1;
-    public final static int REVISION = 7;
-    public final static String SUBREV = ".4";
-	public final static String releaseDate = "2019-10-24";
+    public final static int REVISION = 8;
+    public final static String SUBREV = ".2";
+	public final static String releaseDate = "2019-11-04";
 	public final static String releaseYear = "2019";
 	public final static String releaseLicence = "Lesser General Public License";
 	public final static String releaseLicenceMini = "LGPL";

diuf/sudoku/gui/EmptyRectangle.html

@@ -1,7 +1,7 @@
 <html>
  <body>
-  <b>Empty Rectangle</b>: The Sudoku requires an Empty rectangle to solve.
+  <b>Empty Rectangle</b>: The Sudoku requires an 2 strong links one of which is an Empty rectangle to solve.
   No skyscrapers, 2-String Kites or XY-Wings allowed.
-  Rating: 4.2
+  Rating: 4.3
  </body>
 </html>