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Beginner Topic 9 of 51 Algorithms

Selection Sort

Repeatedly selecting the minimum from the unsorted part.

How it works

Selection sort divides the array into a sorted prefix and an unsorted remainder. On each pass it scans the remainder for the minimum element and swaps it into the next position of the prefix. It always makes O(n squared) comparisons regardless of input order, but performs at most n minus 1 swaps, and the standard version is not stable.

Where it is used

Selection sort is useful when writes are far more expensive than reads, such as on flash memory, and for teaching. It is simple to implement and has predictable behavior on any input.

Common pitfall

It does not benefit from partially sorted data, since it always scans everything. Swapping can break the relative order of equal elements, which matters when sorting records by multiple keys. For anything beyond small arrays, choose merge sort, quicksort or the built-in sort.

Where it fits in the course

Selection Sort is topic 9 of 51 in Algorithms, rated Beginner. It follows Bubble Sort. The next topic is Insertion Sort.

Practice and explore

How to study this topic

  1. Read the explanation above and restate the definition in your own words.
  2. Open the interactive lesson and answer its mini quiz.
  3. Read the common pitfall, then write a short example that avoids it.
  4. Check your understanding in the Algorithms quiz, and revisit the topic if you miss a question.

Frequently asked questions

What is Selection Sort?
Repeatedly selecting the minimum from the unsorted part. It belongs to Algorithms and is a beginner-level topic.
Where do people use Selection Sort?
Selection sort is useful when writes are far more expensive than reads, such as on flash memory, and for teaching.
What is the most common mistake with Selection Sort?
It does not benefit from partially sorted data, since it always scans everything.
What should I learn before this topic?
Start with Bubble Sort, the topic just before it in Algorithms.
How can I practice it?
Answer the mini quiz in the interactive lesson, then take the Algorithms quiz. You can also explore Sorting Algorithms in the Visual Lab.
Is Selection Sort hard to learn?
It is a Beginner topic, so it works as an entry point. If the terms are new, read the explanation twice and try the visualizer before the quiz.
How long does it take to learn Selection Sort?
Most learners can read the explanation and finish the interactive lesson in under an hour. Fluency comes from applying the idea, so plan a few short practice sessions with the quiz.
Which topics are related to Selection Sort?
Bubble Sort, Insertion Sort, Binary Search are closely connected. The full list is in the related topics section of this page.
What should I study after Selection Sort?
Continue with Insertion Sort, the next topic in Algorithms.

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