Tag: data-structures
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Most referenced — #data-structures
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Quadtree
A tree where each internal node has exactly four children, recursively partitioning 2D space for efficient spatial queries.
3mo ago
Data Structures advanced
Suffix Array
PHP 7.0+ A sorted array of all suffix starting positions of a string, enabling fast substring search in O(m log n) with far less memory than a suffix tree.
4mo ago
Algorithms advanced
Merkle Tree
PHP 7.0+
A binary tree where each non-leaf node holds the hash of its children, enabling efficient verification that data is intact and untampered.
4mo ago
Data Structures advanced
Fenwick Tree (Binary Indexed Tree)
PHP 7.4+
1
A compact array-backed structure giving O(log n) prefix-sum queries and O(log n) point updates with minimal code and memory overhead.
5mo ago
Data Structures advanced
Trie (Prefix Tree)
A tree where each node represents a character — paths from root to leaf spell out keys, enabling O(m) lookup, prefix search, and autocomplete where m is key length, independent of dataset size.
7mo ago
Data Structures intermediate
Inverted Index
8
A data structure that maps each unique word to the list of documents containing it — the foundation of all full-text search engines, enabling fast lookup of documents matching a query term.
7mo ago
Search intermediate
Redis
PHP 7.0+
5
An in-memory key-value data store used in PHP applications for caching, session storage, queues, rate limiting, and pub/sub — providing sub-millisecond data access compared to database queries.
7mo ago
Performance beginner
SPL Introduction — Standard PHP Library
PHP 5.0+
SPL (Standard PHP Library, PHP 5.0) added data structures, iterators, and interfaces — SplStack, SplQueue, SplHeap, ArrayObject, and the Iterator/Countable interfaces.
7mo ago
PHP intermediate
Adjacency Matrix vs Adjacency List
1
Two ways to represent a graph — adjacency matrix (2D array, O(1) edge lookup, O(V²) space) vs adjacency list (array of lists, O(V+E) space, better for sparse graphs).
7mo ago
Data Structures intermediate
B-Trees & B+ Trees
5
Self-balancing tree structures used in database indexes — each node holds multiple keys, keeping the tree shallow and minimising disk I/O for range queries.
7mo ago
Data Structures advanced
Circular Buffer / Ring Buffer
PHP 5.0+
1
A fixed-size array treated as circular — the write pointer wraps around when it reaches the end, overwriting the oldest data. Used for logs, audio streaming, and producer-consumer queues.
7mo ago
Data Structures intermediate
Disjoint Set / Union-Find
A data structure tracking which elements belong to the same group — supporting near-O(1) union and find operations. Used for network connectivity, Kruskal's MST, and cycle detection.
7mo ago
Data Structures advanced
Graphs
3
A collection of nodes (vertices) connected by edges — directed or undirected, weighted or unweighted. The most general data structure, modelling networks, dependencies, and relationships.
7mo ago
Data Structures intermediate
Queues
PHP 5.3+ A FIFO (First In, First Out) data structure — the first element enqueued is the first dequeued. Used for BFS traversal, job queues, rate limiting, and buffer management.
7mo ago
Data Structures beginner
Segment Trees
A tree data structure for O(log n) range queries and point updates — supporting sum, min, max over arbitrary array ranges.
7mo ago
Data Structures advanced
Skip Lists
4
A probabilistic data structure providing O(log n) search, insert, and delete — used internally in Redis sorted sets for ZADD/ZRANGE operations.
7mo ago
Data Structures advanced
Sparse Matrix Representations
COO, CSR, and DOK formats efficiently store matrices where most values are zero — avoiding storing terabytes of zeros for recommendation systems and graphs.
7mo ago
Data Structures advanced
Stacks
PHP 5.3+ A LIFO (Last In, First Out) data structure — the last element pushed is the first popped. Used for function call stacks, undo history, expression parsing, and DFS traversal.
7mo ago
Data Structures beginner
Tries (Prefix Trees)
PHP 5.0+
A tree where each path from root to node spells a prefix — enabling O(m) insert, lookup, and prefix search where m is the string length, regardless of dictionary size.
7mo ago
Data Structures advanced
Arrays
PHP 5.0+
10
The most fundamental data structure — a contiguous block of memory holding elements of the same type, offering O(1) index access but O(n) insertion and deletion in the middle.
7mo ago
Data Structures beginner