What is the advantage of a hash table compared to an array in terms of data access speed?

The advantage of a hash table (e.g., Dictionary in C#) over an array is the speed of data access by key.

• In an array, access to an element by index is an O(1) operation, but if you need to find an element by value or key, you have to iterate through the elements — O(n).
• In a hash table, access to an element by key is usually performed in amortized O(1) time, thanks to the computation of the hash code of the key and quick search.

Thus, if fast search, insertion, and deletion by key are required, a hash table is significantly more efficient than an array.