One way to solve collision problems in hash tables is to use a technique called chaining. In chaining, each index in the hash table is a linked list, and when a collision occurs, the new key-value pair is added to the end of the list. This allows for multiple key-value pairs to be stored at the same index without causing any overlap.
Another solution is to use open addressing, where the hash table does not use linked lists to store data. Instead, when a collision occurs, the hash table will search for the next available empty index to store the key-value pair. This can be done using a linear probing or a quadratic probing approach.
In linear probing, the hash table will search for the next empty index by incrementing the index by 1 until it finds an empty slot. This can lead to clustering, where a group of occupied indices are stored together, which can decrease the efficiency of the hash table.
Quadratic probing is similar to linear probing, but instead of incrementing the index by 1, it increments it by a fixed number, such as 2 or 3. This helps to avoid clustering and can be more efficient than linear probing.
Swift offers several options for implementing hash tables. The Dictionary and Set types in Swift use a hash table implementation under the hood and handle collisions automatically. However, if you want to implement your own hash table, you can use an array and handle collisions using chaining or open addressing.
Let's take a look at examples of these techniques:
Notice how both keys, 'c' and 'w', point to the identical index, 17.