code: @Override
      final void remove(int n, int m) {
          m1[n] = m2[m] = UNMAPPED;
          size = size - 1;
          for (int w : g1[n])
              if (t1[w] > size) t1[w] = 0;
          for (int w : g2[m])
              if (t2[w] > size) t2[w] = 0;
      }
docs: {@inheritDoc}