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A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
Quadtree
A tree where each internal node has exactly four children, recursively partitioning 2D space for efficient spatial queries.
3mo ago Data Structures 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
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
Diagram: Queues 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
Diagram: Stacks 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
Diagram: Binary Trees Binary Trees PHP 5.0+ 🧠 5
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.
7mo ago Data Structures intermediate
Diagram: Bloom Filter 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.
7mo ago Data Structures advanced
Diagram: Hash Table Hash Table PHP 5.0+ 🧠 3
A data structure that maps keys to values using a hash function, providing amortised O(1) average-case lookups, insertions, and deletions.
7mo ago Data Structures intermediate
Diagram: Heaps & Priority Queues Heaps & Priority Queues PHP 5.3+ 🧠 2
A tree-based structure satisfying the heap property — min-heap: parent ≤ children; max-heap: parent ≥ children — enabling O(1) peek and O(log n) insert/extract for priority queues.
7mo ago Data Structures intermediate
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