7 Core Data Structures That Power Modern Software

1. Array (List)

Ordered collection where each element has an index, providing O(1) random access.

Application scenario : Fast data access when the data size is relatively small.

Advantages : Direct indexing yields constant‑time access.

Disadvantages : Fixed size after creation; insertions and deletions require shifting elements, resulting in O(n) cost.

2. Queue

First‑In‑First‑Out (FIFO) structure where elements are enqueued at the tail and dequeued from the head.

Application scenario : Ordered processing of tasks such as print‑job queues.

Advantages : Guarantees chronological processing order.

Disadvantages : No random access to interior elements.

3. Stack

Last‑In‑First‑Out (LIFO) structure where the most recently added element is at the top.

Application scenario : Back‑tracking operations and recursion.

Advantages : Simple to use; top element is quickly accessible.

Disadvantages : Only the top element can be accessed.

4. Linked List

Sequence of nodes where each node stores data and a reference to the next node.

Application scenario : Frequent insertions and deletions.

Advantages : Insertion and deletion are O(1) when the node is known; no element shifting.

Disadvantages : Traversal from the head is required for element access, leading to O(n) lookup.

5. Tree

Non‑linear hierarchical structure with a root, internal nodes, and leaves.

Application scenario : Representing hierarchical relationships such as file‑system directories.

Advantages : Enables fast search (e.g., O(log n) in balanced binary trees) and efficient organization.

Disadvantages : More complex; additional storage for pointers.

6. Graph

Collection of vertices (nodes) and edges (connections) that can model arbitrary relationships.

Application scenario : Modeling complex networks such as traffic flows or social networks.

Advantages : Flexible representation of non‑linear connections.

Disadvantages : Algorithms often have high time and space complexity for large graphs.

7. Hash Table

Structure that maps keys to array indices via a hash function, providing near‑constant‑time lookup, insertion, and deletion.

Application scenario : Fast lookup, insertion, and deletion, e.g., database indexes or caches.

Advantages : Typically O(1) access speed.

Disadvantages : Collisions occur when distinct keys map to the same index; resolution strategies add complexity and may affect performance.

Code example

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