** Rehashing**

If a fixed-size hash table is used with some secondary hash function
to deal with collisions, the number of comparisons will become
larger as *λ* increases, with a knee around *λ = 0.7* .

When this happens, it will be necessary to expand the array by:

- making a new array, larger by a factor of 1.5 or 2.
- rehashing all elements of the existing array into the new array.
- replacing the old array by the new one, letting the old one be garbage-collected.

The rehashing process is *O(n)*, but only has to be done once every
*n* times, so its amortized cost is *O(1)*.