Select a suitable data structure (1D or 2D array) to use for a given task

What is an Array?

An array is a collection of items stored in contiguous memory locations. Think of it as a row of lockers, each holding a single item. The items are accessed by an index (starting at 0).

Arrays can be:

• 1‑D (one‑dimensional) – a single row of items.
• 2‑D (two‑dimensional) – a grid of rows and columns, like a spreadsheet.

Analogy: The Library 📚

Imagine a library:

• 1‑D array is a single shelf of books. You pick a book by its position on that shelf.
• 2‑D array is the whole library with rows of shelves. You locate a book by row and column.

When to Use a 1‑D Array

1. Data is a simple list (e.g., student grades, daily temperatures).
2. Only one dimension of variation is needed.
3. Memory is limited – a single row is smaller than a grid.

Example: Storing the scores of 10 students in a single test.

When to Use a 2‑D Array

1. Data has two independent dimensions (e.g., rows of students and columns of subjects).
2. Operations involve both dimensions (e.g., calculating row totals and column averages).
3. You need to represent a matrix or grid (e.g., a chessboard, seating chart).

Example: A timetable where each cell holds a class for a specific day and period.

Decision Tree: Pick the Right Array

1. Does the problem involve one list of items? → Use 1‑D.
2. Are there two independent categories (e.g., rows and columns)? → Use 2‑D.
3. Do you need to perform matrix operations (multiplication, transposition)? → 2‑D.
4. Is memory a concern and you only need a single dimension? → 1‑D.

Exam Tips 📌

• Read the question carefully: look for keywords like “grid”, “matrix”, or “single list”.
• Sketch a quick diagram: a row of boxes for 1‑D, a grid for 2‑D.
• Remember that array indices start at 0 in most programming languages.
• When in doubt, ask: “How many independent ways can I access the data?”

Quick Test 🚀

Choose the appropriate array type for each scenario:

1. Storing the names of 30 students in a class.
2. Representing a 5×5 tic‑tac‑toe board.
3. Keeping track of the temperature for each hour of a 24‑hour day.
4. Recording the scores of 12 students across 4 subjects.

Answers: 1) 1‑D, 2) 2‑D, 3) 1‑D, 4) 2‑D.