introduce bitloops

src/main/java/puzzle/Export.java

@@ -1,6 +1,7 @@
 package puzzle;
 
 import lombok.Getter;
+import lombok.NoArgsConstructor;
 import lombok.experimental.Accessors;
 import lombok.experimental.Delegate;
 import lombok.val;
@@ -339,13 +340,18 @@ public record Export() {
    
    @Getter
    @Accessors(fluent = true)
+   @NoArgsConstructor
    static final class IntListDTO {
       
       int[] data = new int[8];
       int   size = 0;
+      public IntListDTO(int size) {
+         data = new int[size];
+      }
       void add(int v) {
          if (size >= data.length) data = Arrays.copyOf(data, data.length * 2);
          data[size++] = v;
       }
+      int[] toArray() { return Arrays.copyOf(data, size); }
    }
 }