A simple type of hash table in which there is a one-to-one mapping between all possible keys and positions in the table. Since no two keys map to the same position, there is no need for collision resolution. However, if there are many possible keys, the table will be large. Generally, direct addressing works well when the universe of possible keys is small.

A common class of random number generators. Understanding the principles behind random number generators can help in devising good hash functions.

An alternative to linear probing and double hashing for probing an open-addressed hash table. In quadratic probing, the sequence of positions probed is determined using a quadratic-form hash function. In general, quadratic probing performs better than linear probing, but it does not perform as well as double hashing. Quadratic probing results in secondary clustering , a form of clustering that is less severe than the primary clustering of linear probing.

A hashing method in which hashing functions are generated randomly at runtime so that no particular set of keys is likely to produce a bad distribution of elements in the hash table. Because the hash functions are generated randomly, even hashing the same set of keys during different executions may result in different measures of performance.