
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. 


 
 function partition($list, $left, $right, $pivotIndex) {   
     $pivotValue = $list[$pivotIndex]
     $list[$pivotIndex], $list[$right] = $list[$right], $list[$pivotIndex]
     $storeIndex = $left
     foreach ($i in $left..($right-1)) {
         if ($list[$i] -lt $pivotValue) {
             $list[$storeIndex],$list[$i] = $list[$i], $list[$storeIndex]
             $storeIndex += 1
         }
     }
     $list[$right],$list[$storeIndex] = $list[$storeIndex], $list[$right]
     $storeIndex
}
 
function rank($list, $left, $right, $n) {
    if ($left -eq $right) {$list[$left]}
    else {
        $pivotIndex = Get-Random -Minimum $left -Maximum $right
        $pivotIndex = partition $list $left $right $pivotIndex
        if ($n -eq $pivotIndex) {$list[$n]}
        elseif ($n -lt $pivotIndex) {(rank $list $left ($pivotIndex - 1) $n)}
        else {(rank $list ($pivotIndex+1) $right $n)}
    }
}
 
function quickselect($list) {
    $right = $list.count-1
    foreach($left in 0..$right) {rank $list $left $right $left}  
}
$arr = @(9, 8, 7, 6, 5, 0, 1, 2, 3, 4)
"$(quickselect $arr)"
 