Is it possible to use the same values as unique identifiers when used as keys in a data structure?

In data structures where keys must be unique (for example, in dictionaries or hash tables), using the same values as keys is not allowed. Keys must unambiguously identify elements.

If you try to add an element with a key that already exists, it usually results in updating the value for that key, rather than adding a new one.

Example in C# using Dictionary:

var dict = new Dictionary<int, string>();
dict[1] = "First";
dict[1] = "Updated first"; // overwrites the value for key 1

Keys must be unique; otherwise, data will be overwritten.

Thus, for unique identification of elements, keys must be unique.