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SingaporeComputer Science

Data Structures

6 dot points across 6 inquiry questions. Click any dot point for a focused answer with worked past exam questions where available.

How are arrays and records stored, and why is array access so fast?

Describe arrays and records as data structures, explain constant-time array indexing and contrast static with dynamic arrays
A focused answer to the H2 Computing outcome on arrays and records. Contiguous storage and constant-time indexing, one and two dimensional arrays, records as fields of mixed type, and static versus dynamic arrays.
8 min answer →

How does a binary search tree keep data ordered for fast search, and why does balance matter?

Describe a binary search tree, perform insertion, search and in-order traversal, and explain how balance affects complexity
A focused answer to the H2 Computing outcome on binary search trees. The ordering property, inserting and searching nodes, in-order traversal giving sorted output, and why an unbalanced tree degrades to O(n).
9 min answer →

How do we represent a graph in a program, and when is an adjacency matrix better than an adjacency list?

Describe graphs and their terminology, represent them as adjacency matrices and adjacency lists, and compare the two representations
A focused answer to the H2 Computing outcome on representing graphs. Vertices and edges, directed and weighted graphs, adjacency matrix versus adjacency list, and the space and lookup trade-offs between them.
8 min answer →

How does a hash table achieve near constant-time lookup, and how are collisions handled?

Describe a hash table and hash function, explain collision resolution by chaining and open addressing, and analyse the effect of load factor
A focused answer to the H2 Computing outcome on hash tables. Hash functions mapping keys to buckets, average O(1) lookup, collisions resolved by chaining or open addressing, and how the load factor affects performance.
9 min answer →

How does a linked list store a sequence using pointers, and how does it differ from an array?

Describe a linked list as nodes joined by pointers, implement insertion and deletion, and contrast it with an array
A focused answer to the H2 Computing outcome on linked lists. Nodes and pointers, traversal, inserting and deleting nodes by relinking, and the trade-offs against arrays for access and modification.
8 min answer →

How do stacks and queues control the order items are added and removed, and where are they used?

Describe stacks (LIFO) and queues (FIFO), implement their core operations, and identify suitable applications of each
A focused answer to the H2 Computing outcome on stacks and queues. The LIFO stack and FIFO queue, their push, pop, enqueue and dequeue operations with overflow and underflow, and typical applications of each.
8 min answer →