introduce bitloops

src/main/java/puzzle/LongArrayList.java

@@ -0,0 +1,30 @@
+package puzzle;
+
+import java.util.Arrays;
+public final class LongArrayList {
+   
+   private long[] a;
+   private int    size;
+   
+   public LongArrayList() { this(16); }
+   
+   public LongArrayList(int initialCapacity) {
+      if (initialCapacity < 0) throw new IllegalArgumentException();
+      a = new long[initialCapacity];
+   }
+   
+   public int size() { return size; }
+   
+   public void add(long v) {
+      if (size == a.length) grow();
+      a[size++] = v;
+   }
+   
+   private void grow() {
+      int    newCap = a.length == 0 ? 1 : a.length * 2;
+      long[] n      = new long[newCap];
+      System.arraycopy(a, 0, n, 0, size);
+      a = n;
+   }
+   public long[] toArray() { return Arrays.copyOf(a, this.size); }
+}