
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


Sort an array of integers (of any convenient size) into ascending order using Circlesort.

In short, compare the first element to the last element, then the second element to the second last element, etc.

Then split the array in two and recurse until there is only one single element in the array, like this:

Before:
6 7 8 9 2 5 3 4 1
After:
1 4 3 5 2 9 8 7 6

Repeat this procedure until quiescence (i.e. until there are no swaps).

Show both the initial, unsorted list and the final sorted list. (Intermediate steps during sorting are optional.)

Optimizations (like doing 0.5 log2(n) iterations and then continue with an Insertion sort) are optional. 


Pseudo code:

 function circlesort (index lo, index hi, swaps)
 {
   if lo == hi return (swaps)
   high := hi
   low := lo
   mid := int((hi-lo)/2)
   while lo < hi {
     if  (value at lo) > (value at hi) {
        swap.values (lo,hi)
        swaps++
     }
     lo++
     hi--
   }
   if lo == hi
     if (value at lo) > (value at hi+1) {
         swap.values (lo,hi+1)
         swaps++
     }
   swaps := circlesort(low,low+mid,swaps)
   swaps := circlesort(low+mid+1,high,swaps)
   return(swaps)
 }
 while circlesort (0, sizeof(array)-1, 0)



See also

 For more information on Circle sorting, see Sourceforge.


' version 21-10-2016
' compile with: fbc -s console
' for boundry checks on array's compile with: fbc -s console -exx
' converted pseudo code into FreeBASIC code
 
' shared variables need to be declared before first use
Dim Shared As Long cs(-7 To 7)
 
Function circlesort(lo As Long, hi As Long, swaps As ULong) As ULong
 
    ' array is declared shared 
    ' sort from lower bound to the highter bound
    ' array's can have subscript range from -2147483648 to +2147483647
 
    If lo = hi Then Return swaps
 
    Dim As Long high = hi
    Dim As Long low = lo
    Dim As Long mid_ = (hi - lo) \ 2
 
    While lo < hi
        If cs(lo) > cs(hi) Then
            Swap cs(lo), cs(hi)
            swaps += 1
        End If
        lo += 1
        hi -= 1
    Wend
    If lo = hi Then
        If cs(lo) > cs(hi +1) Then
            Swap cs(lo), cs(hi +1)
            swaps += 1
        End If
    End If
    swaps = circlesort(low          , low + mid_, swaps)
    swaps = circlesort(low + mid_ +1,       high, swaps)
 
    Return swaps
 
End Function
 
' ------=< MAIN >=------
 
Dim As Long i, a = LBound(cs), b = UBound(cs)
 
Randomize Timer
For i = a To b : cs(i) = i  : Next
For i = a To b ' little shuffle
    Swap cs(i), cs(Int(Rnd * (b - a +1)) + a)
Next
 
Print "unsorted ";
For i = a To b : Print Using "####"; cs(i); : Next : Print
 
' sort the array, loop until sorted
While circlesort(a, b, 0) : Wend
 
Print "  sorted ";
For i = a To b : Print Using "####"; cs(i); : Next : Print
 
' empty keyboard buffer
While InKey <> "" : Wend
Print : Print "hit any key to end program"
Sleep
End