What is the characteristic of the search speed of elements in the Dictionary data structure?

In a Dictionary data structure (for example, in C#), searching for an element by key usually has an amortized complexity of O(1), meaning it is very fast and practically constant in time.

This is achieved by using a hash table, where the key is transformed into a hash code, which quickly finds the index in the array.

However, in the worst case (for example, with a large number of collisions), the search time can degrade to O(n), where n is the number of elements, but such situations are rare with good hash function distribution.

Example of searching in a Dictionary in C#:

var dict = new Dictionary<string, int>();
dict["apple"] = 5;
int value = dict["apple"]; // Search in O(1)