The Ford-Johnson algorithm[1], also known as the merge-insertion sort[2,3] uses the minimum number of possible comparisons for lists of 22 items or less, and at the time of writing has the fewest comparisons known for lists of 46 items or less. It is therefore very well suited for cases where comparisons are expensive, such as user input, and the API is implemented to take an async comparator function for this reason.
import { mergeInsertionSort, Comparator } from 'merge-insertion'
// A Comparator should return 0 if the first item is larger, or 1 if the second item is larger.
const comp :Comparator<string> = async ([a, b]) => a > b ? 0 : 1
// Sort five items in ascending order with a maximum of only seven comparisons:
const sorted = await mergeInsertionSort(['D', 'A', 'B', 'E', 'C'], comp)- Ford, L. R., & Johnson, S. M. (1959). A Tournament Problem. The American Mathematical Monthly, 66(5), 387–389. https://doi.org/10.1080/00029890.1959.11989306
- Knuth, D. E. (1998). The Art of Computer Programming: Volume 3: Sorting and Searching (2nd ed.). Addison-Wesley. https://cs.stanford.edu/~knuth/taocp.html#vol3
- https://en.wikipedia.org/wiki/Merge-insertion_sort
Comparable =
NonNullable<unknown>
A type of object that can be compared by a Comparator and therefore sorted by mergeInsertionSort. Must have sensible support for the equality operators.
Comparator<
T> = (ab) =>Promise<0|1>
A user-supplied function to compare two items.
T extends Comparable
Readonly<[T, T]>
A tuple of the two items to be compared; they must not be equal.
Promise<0 | 1>
Must return a Promise resolving to 0 if the first item is ranked higher, or 1 if the second item is ranked higher.
mergeInsertionMaxComparisons(
n):number
Returns the maximum number of comparisons that mergeInsertionSort will perform depending on the input length.
number
The number of items in the list to be sorted.
number
The expected maximum number of comparisons.
mergeInsertionSort<
T>(array,comparator):Promise<T[]>
Merge-Insertion Sort (Ford-Johnson algorithm) with async comparison.
T extends object
The type of the items to sort.
readonly T[]
Array of to sort. Duplicate items are not allowed.
Comparator<T>
Async comparison function.
Promise<T[]>
A Promise resolving to a shallow copy of the array sorted in ascending order.
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