introduce bitloops

src/main/java/puzzle/Export.java

@@ -45,11 +45,15 @@ public record Export() {
    static int INDEX(int r, int cols, int c) { return r * cols + c; }
    @AllArgsConstructor
    enum Clue {
-      DOWN(CLUE_DOWN),
-      RIGHT(CLUE_RIGHT),
-      UP(CLUE_UP),
-      LEFT(CLUE_LEFT);
+      DOWN(CLUE_DOWN, 'B', 'b'),
+      RIGHT(CLUE_RIGHT, 'A', 'a'),
+      UP(CLUE_UP, 'C', 'c'),
+      LEFT(CLUE_LEFT, 'D', 'd'),
+      NONE(CLUE_LEFT, '?', '?');
       final byte dir;
+      final char slotChar, clueChar;
+      private static final Clue[] CLUES = new Clue[]{ DOWN, RIGHT, UP, LEFT, NONE, NONE, NONE, NONE, NONE };
+      public static Clue from(int dir) { return CLUES[dir]; }
    }
    
    record Strings() {
@@ -295,7 +299,7 @@ public record Export() {
                  p.arrowCol() - MIN_C,
                  p.isReversed(), bytes
          )).toArray(WordOut[]::new);
-         var total    = 0.0001d;
+         var total = 0.0001d;
          for (var word : wordsOut) {
             total += word.complex();
          }