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).