
Sorting Algorithm

This is a sorting algorithm.   It may be applied to a set of data in order to sort it.    
For comparing various sorts, see compare sorts.  
For other sorting algorithms,   see sorting algorithms,   or:

O(n logn) sorts
Heap sort |
Merge sort |
Patience sort |
Quick sort
O(n log2n) sorts
Shell Sort
O(n2) sorts
Bubble sort |
Cocktail sort |
Cocktail sort with shifting bounds |
Comb sort |
Cycle sort |
Gnome sort |
Insertion sort |
Selection sort |
Strand sort
other sorts
Bead sort |
Bogo sort |
Common sorted list |
Composite structures sort |
Custom comparator sort |
Counting sort |
Disjoint sublist sort |
External sort |
Jort sort |
Lexicographical sort |
Natural sorting |
Order by pair comparisons |
Order disjoint list items |
Order two numerical lists |
Object identifier (OID) sort |
Pancake sort |
Quickselect |
Permutation sort |
Radix sort |
Ranking methods |
Remove duplicate elements |
Sleep sort |
Stooge sort |
[Sort letters of a string] |
Three variable sort |
Topological sort |
Tree sort


Use the quickselect algorithm on the vector

 [9, 8, 7, 6, 5, 0, 1, 2, 3, 4]
To show the first, second, third, ... up to the tenth largest member of the vector, in order, here on this page.

 Note: Quicksort has a separate task. 


 
-module(quickselect).
 
-export([test/0]).
 
 
test() ->
    V = [9, 8, 7, 6, 5, 0, 1, 2, 3, 4],
    lists:map(
        fun(I) -> quickselect(I,V) end, 
        lists:seq(0, length(V) - 1)
    ).
 
quickselect(K, [X | Xs]) ->
    {Ys, Zs} = 
        lists:partition(fun(E) -> E < X end, Xs),
    L = length(Ys),
    if 
        K < L -> 
            quickselect(K, Ys);
        K > L -> 
            quickselect(K - L - 1, Zs);
        true -> 
            X
    end. 
 