
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. 


 
Procedure QuickPartition (Array L(1), left, right, pivotIndex)
     pivotValue = L(pivotIndex)
     Swap L(pivotIndex) , L(right); Move pivot To End
     storeIndex = left
     For i=left To right-1
         If L(i) < pivotValue
             Swap L(storeIndex),L(i)
             storeIndex+1
         EndIf
     Next i
     Swap L(right), L(storeIndex)  ; Move pivot To its final place
     ProcedureReturn storeIndex
 EndProcedure
Procedure QuickSelect(Array L(1), left, right, k)
    Repeat
         If left = right:ProcedureReturn L(left):EndIf
         pivotIndex.i= left; Select pivotIndex between left And right
         pivotIndex= QuickPartition(L(), left, right, pivotIndex)
         If k = pivotIndex
             ProcedureReturn L(k)
         ElseIf k < pivotIndex
             right= pivotIndex - 1
         Else
             left= pivotIndex + 1
         EndIf
    ForEver
EndProcedure
Dim L.i(9)
For i=0 To 9
    Read L(i)
Next i
DataSection
    Data.i 9, 8, 7, 6, 5, 0, 1, 2, 3, 4
EndDataSection
For i=0 To 9
    Debug QuickSelect(L(),0,9,i)
Next i