introduce bitloops

src/test/java/puzzle/SwedishGeneratorTest.java

@@ -161,6 +161,37 @@ public class SwedishGeneratorTest {
       assertTrue(Slot.horiz(2)); // right
       assertFalse(Slot.horiz(3)); // down
    }
+   static int intersectSorted(int[] a, int aLen, int[] b, int bLen, int[] out) {
+      if (aLen == 0 || bLen == 0) return 0;
+      if (aLen < bLen >>> 4) {
+         int k = 0;
+         for (int i = 0; i < aLen; i++) {
+            int x = a[i];
+            if (Arrays.binarySearch(b, 0, bLen, x) >= 0) out[k++] = x;
+         }
+         return k;
+      }
+      if (bLen < aLen >>> 4) {
+         int k = 0;
+         for (int i = 0; i < bLen; i++) {
+            int y = b[i];
+            if (Arrays.binarySearch(a, 0, aLen, y) >= 0) out[k++] = y;
+         }
+         return k;
+      }
+      int i = 0, j = 0, k = 0, x, y;
+      while (i < aLen && j < bLen) {
+         x = a[i];
+         y = b[j];
+         if (x == y) {
+            out[k++] = x;
+            i++;
+            j++;
+         } else if (x < y) i++;
+         else j++;
+      }
+      return k;
+   }
    
    @Test
    void testIntersectSorted() {