  SparseSet(Zone* zone, int capacity)
      : capacity_(capacity),
        length_(0),
        dense_(zone->NewArray<int>(capacity)),
        sparse_(zone->NewArray<int>(capacity)) {
#ifndef NVALGRIND
    // Initialize the sparse array to make valgrind happy.
    memset(sparse_, 0, sizeof(sparse_[0]) * capacity);
#endif
  }
  SparseSet(Zone* zone, int capacity)
      : capacity_(capacity),
        length_(0),
        dense_(zone->NewArray<int>(capacity)),
        sparse_(zone->NewArray<int>(capacity)) {
#ifndef NVALGRIND
     
    memset(sparse_, 0, sizeof(sparse_[0]) * capacity);
#endif
  }