3.9 Developing Algorithms

Three algorithm-building strategies

Developers use different strategies depending on the problem: sequential algorithms perform steps in order, one after another; parallel algorithms run multiple instructions simultaneously across processors; and algorithms that use iteration repeat a set of steps until a condition is met (e.g., checking every item in a list).

Sequencing, selection, and iteration

All algorithms are built from combinations of sequencing (ordered steps), selection (using conditionals like if/else to choose a path), and iteration (loops that repeat steps). Combining these building blocks lets programmers create algorithms that solve a wide range of problems, from simple calculations to complex data processing.

Choosing the right strategy

The best strategy depends on the task: a sequential algorithm works for straightforward, ordered tasks; a parallel algorithm speeds up work that can be split into independent subtasks (like searching different sections of data at once); and iterative approaches efficiently handle repetitive tasks such as searching or summing a list.

Key terms

Sequential algorithm

An algorithm where steps are executed one after another, in order.

Parallel algorithm

An algorithm that executes multiple instructions simultaneously, often to save time.

Iteration

A programming building block that repeats a set of steps until a condition is met (loops).

Selection

A building block that uses conditionals (if/else) to choose between different paths in an algorithm.

Sequencing

A building block where instructions are carried out in a specific, linear order.

Try an AP-style question

Which three building blocks can express every algorithm?

1. Input, output, and storage
2. Sequencing, selection, and iteration
3. Variables, lists, and strings
4. Compression, encryption, and search