Tag: data-structures
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Most referenced — #data-structures
Graphs 2Inverted Index 2Graph Algorithms 2Heaps & Priority Queues 2Binary Trees 2Segment Trees 2Adjacency Matrix vs Adjacency List 1Hash Table 1
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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.
2w 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.
2w 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.
1mo 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.
3mo ago
Data Structures intermediate
Inverted Index
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.
3mo ago
Search intermediate
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.
3mo 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).
3mo ago
Data Structures intermediate
B-Trees & B+ Trees
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.
3mo 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.
3mo 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.
3mo 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.
3mo 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.
3mo 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.
3mo ago
Data Structures advanced
Skip Lists
A probabilistic data structure providing O(log n) search, insert, and delete — used internally in Redis sorted sets for ZADD/ZRANGE operations.
3mo 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.
3mo 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.
3mo 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.
3mo 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.
3mo ago
Data Structures beginner
Binary Trees
PHP 5.0+
4
A hierarchical structure where each node has at most two children — Binary Search Trees enable O(log n) search, while balanced variants (AVL, Red-Black) guarantee it.
3mo ago
Data Structures intermediate
Bloom Filter
PHP 7.0+ A probabilistic data structure that tests set membership in O(1) time and O(1) space, with a tunable false-positive rate and zero false negatives.
3mo ago
Data Structures advanced