How to determine the optimal size of a hash table to minimize the number of collisions?

The optimal size of a hash table is usually chosen to minimize collisions while efficiently using memory. Main recommendations:

• Choose the table size as a prime number to distribute keys more evenly across buckets.
• The size should be proportional to the expected number of elements, considering the load factor, typically 0.7-0.75.

For example, if 1000 elements are expected, the table size can be around 1300-1500 (a prime number) to keep the load factor around 0.7.

Example calculation:

size_t expected_elements = 1000;
float load_factor = 0.75f;
size_t table_size = next_prime(static_cast<size_t>(expected_elements / load_factor));

Where next_prime is a function that finds the nearest prime number greater than or equal to the argument.

Thus, choosing the correct hash table size and maintaining the load factor helps minimize collisions and improve performance.