Is a data structure with indexes necessarily a binary tree?

No, an indexed data structure does not necessarily have to be a binary tree. Indices can be implemented using various data structures depending on performance requirements and the type of operations.

For example:

• Arrays and lists — simple structures with indices by position.
• Hash tables — provide quick access by key, but are not trees.
• B-trees and B+-trees — used in databases for indexing, but these are not necessarily binary trees.
• Binary trees — one of the possible structures where each node has no more than two children.

Thus, an indexed data structure can be implemented not only as a binary tree but also with other structures suitable for specific tasks.