What is a heap in data structures?

A heap is a specialized tree-based data structure that is designed to maintain a specific order between its elements according to the heap property. This property can manifest in two main forms: a max-heap, where the value of each node is greater than or equal to the values of its children, and a min-heap, where the value is less than or equal to its children. This structure allows heaps to efficiently support priority queue operations, such as inserting an element or extracting the highest or lowest priority element.

Heaps are particularly useful in algorithms such as heapsort and in implementing priority queues, where quick access to the highest or lowest element is necessary. Because a heap is often implemented using a binary tree, it maintains a partially ordered structure that supports efficient addition and removal of elements.

In contrast, other options reference different concepts. For instance, linear data structures characterized by sequential storage refer to structures like arrays and linked lists, which do not exhibit the hierarchical properties of a heap. The notion of an array that allows only unique elements is more related to data structures like sets. Lastly, an unorganized list of data elements does not accurately describe a heap, as heaps possess a defined structure and ordering based on the heap property.