
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. 


(seed (in "/dev/urandom" (rd 8)))
(de swapL (Lst X Y)
   (let L (nth Lst Y)
      (swap
         L
         (swap (nth Lst X) (car L)) ) ) )
(de partition (Lst L R P)
   (let V (get Lst P)
      (swapL Lst R P)
      (for I (range L R)
         (and
            (> V (get Lst I))
            (swapL Lst L I)
            (inc 'L) ) )
      (swapL Lst L R)
      L ) )
(de quick (Lst N L R)
   (default L (inc N)  R (length Lst))
   (if (= L R)
      (get Lst L)
      (let P (partition Lst L R (rand L R))
         (cond
            ((= N P) (get Lst N))
            ((> P N) (quick Lst N L P))
            (T (quick Lst N P R)) ) ) ) )
(let Lst (9 8 7 6 5 0 1 2 3 4)
   (println
      (mapcar
         '((N) (quick Lst N))
         (range 0 9) ) ) )