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Beginner Topic 14 of 51 Algorithms

Radix Sort

Sorting digit by digit using a stable subroutine.

How it works

Radix sort processes keys digit by digit, from least significant to most significant, using a stable sort such as counting sort at each digit. After the last pass, the whole list is sorted. For n keys of d digits in base b it takes O(d times (n + b)) time, which beats comparison sorts for fixed-width integers or strings of limited length.

Where it is used

Sorting large sets of integers, IP addresses, dates or fixed-length strings, suffix array construction and GPU sorting use radix sort. It is common in high-performance libraries.

Common pitfall

The inner sort must be stable or the result will be wrong. Variable-length keys need padding or MSD variants. Negative numbers and floating-point values need transformations. Memory usage and cache behavior can make it slower than quicksort for small inputs. Choose the base to balance passes against buckets.

Where it fits in the course

Radix Sort is topic 14 of 51 in Algorithms, rated Beginner. It follows Counting Sort. The next topic is Brute Force.

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 Radix Sort?
Sorting digit by digit using a stable subroutine. It belongs to Algorithms and is a beginner-level topic.
Where do people use Radix Sort?
Sorting large sets of integers, IP addresses, dates or fixed-length strings, suffix array construction and GPU sorting use radix sort.
What is the most common mistake with Radix Sort?
The inner sort must be stable or the result will be wrong.
What should I learn before this topic?
Start with Counting 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 Radix 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 Radix 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 Radix Sort?
Counting Sort, Brute Force, Quick Sort are closely connected. The full list is in the related topics section of this page.
What should I study after Radix Sort?
Continue with Brute Force, the next topic in Algorithms.

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