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Radix Sort

Sorts values by processing one digit or character position at a time.

Quick Facts

Compact metadata for implementation and discovery.

Radix Sort repeatedly groups values by digit position, often using a stable counting sort for each pass.

integer key rangestable orderingdistribution sortordering invariantcomparison or key rulearray rearrangement

Quick facts

Runtime and memory behavior at a glance.

Best

O(d(n + k))

Average

O(d(n + k))

Worst

O(d(n + k))

Space

O(n + k)

Use Radix Sort when you need to process values by digit or character.
Use it for sorting integers with inputs like integer or fixed-width key array.
Use it when ordered output makes later searching, ranking, or presentation easier.
Use it when the Distribution Sort tradeoff is acceptable for the problem size.

Avoid it when values are not bounded integers or cannot be mapped cleanly to integer keys.
Avoid it when a partial order, top-k result, or streaming approach would answer the question with less work.
Avoid it when the required output is not sorted array.

Input: values = [5, 1, 4, 2]
Output: values = [1, 2, 4, 5]
Explanation: Radix Sort: The algorithm reorders the values so later operations can read them in ascending order.

Keep the input contract explicit: Integer or fixed-width key array; Base or digit width.
Use this step as the implementation spine: Choose the order of digit positions.
Then preserve the next state change: For each digit position:.
Test with empty input, one item, duplicates, and already sorted values.

Radix Sort depends on stable digit passes to preserve earlier ordering work.
Assuming stability without checking the implementation can reorder equal keys.
Forgetting to define how equal values and custom comparison rules should behave.
Returning sorted array without handling empty, invalid, or boundary inputs.