Data Structures

Classes of abstract data types such as containers, dictionaries, and priority queues, have many different but functionally equivalent data structures that implement them. These different data structures realize different tradeoffs in the time to execute various operations.

Information on this page is taken from The Algorithm Design Manual by Steven S. Skiena.

Contiguous vs. Linked

Data structures are either contiguous or linked, depending upon whether they are based on arrays or pointers.


The array is the fundamental contiguously-allocated data structures. These single slabs of memory have constant access given the index and space efficiency. Dynamic arrays enable resizing. First, an initial size is allocated. If we run out of space, a larger array (usually 2x) is allocated and the elements are copied over. Insertion amortizes to \(O(1)\).


The list is the simplest linked structure. Each node in the list has data and pointer fields. Pointers are the connections that hold the pieces of together. Pointers represent the address of a location in memory. List don't incur overflow, but require extra space for pointer fields and don't given efficient random access to items.

Abstract Data Types


A container denotes a data structure that permits storage and retrieval of data items independent of content. Containers are distinguished by the particular retrieval order they support. Stacks support retrieval by last-in, first-out (LIFO) order. Queues support retrieval in first in, first out (FIFO) order.

See Bags, Stacks, and Queues for more information.


The dictionary data type permits access to data items by content. Operations include search (when given a key), insert, and delete. Dictionaries are also called maps and associative arrays.

Hash tables are a very practical way to maintain a dictionary.


See Trees for more information.

Priority Queues

Priority queues are data structures that provide more flexibility than simple sorting, because they allow new elements to enter a system at arbitrary intervals. The basic priority queue supports three primary operations: insert, find-minimum/maximum, and delete-minimum/maximum. Priority queues can be implemented with arrays or BSTs, but a particularly nice implementation is the heap.