How to resolve the algorithm Sorting algorithms/Cocktail sort with shifting bounds step by step in the REXX programming language
How to resolve the algorithm Sorting algorithms/Cocktail sort with shifting bounds step by step in the REXX programming language
Table of Contents
Problem Statement
The cocktail sort is an improvement on the Bubble Sort.
A cocktail sort is also known as:
The improvement is basically that values "bubble" (migrate) both directions through the array, because on each iteration the cocktail sort bubble sorts once forwards and once backwards. After ii passes, the first ii and the last ii elements in the array are in their correct positions, and don't have to be checked (again). By shortening the part of the array that is sorted each time, the number of comparisons can be halved.
Pseudocode for the 2nd algorithm (from Wikipedia) with an added comment and changed indentations: % indicates a comment, and deal indicates a swap.
Implement a cocktail sort and optionally show the sorted output here on this page. See the discussion page for some timing comparisons.
Let's start with the solution:
Step by Step solution about How to resolve the algorithm Sorting algorithms/Cocktail sort with shifting bounds step by step in the REXX programming language
Source code in the rexx programming language
/*REXX program sorts an array using the cocktail─sort method with shifting bounds. */
call gen /*generate some array elements. */
call show 'before sort' /*show unsorted array elements. */
say copies('█', 101) /*show a separator line (a fence). */
call cocktailSort # /*invoke the cocktail sort subroutine. */
call show ' after sort' /*show sorted array elements. */
exit /*stick a fork in it, we're all done. */
/*──────────────────────────────────────────────────────────────────────────────────────*/
cocktailSort: procedure expose @.; parse arg N /*N: is number of items. */
end$= N - 1; beg$= 1
do while beg$ <= end$
beg$$= end$; end$$= beg$
do j=beg$ to end$; jp= j + 1
if @.j>@.jp then do; _=@.j; @.j=@.jp; @.jp=_; end$$=j; end
end /*j*/
end$= end$$ - 1
do k=end$ to beg$ by -1; kp= k + 1
if @.k>@.kp then do; _=@.k; @.k=@.kp; @.kp=_; beg$$=k; end
end /*k*/
beg$= beg$$ + 1
end /*while*/
return
/*──────────────────────────────────────────────────────────────────────────────────────*/
gen: @.= /*assign a default value for the stem. */
@.1 = '---the 22 card tarot deck (larger deck has 56 additional cards in 4 suits)---'
@.2 = '==========symbol====================pip======================================'
@.3 = 'the juggler ◄─── I'
@.4 = 'the high priestess [Popess] ◄─── II'
@.5 = 'the empress ◄─── III'
@.6 = 'the emperor ◄─── IV'
@.7 = 'the hierophant [Pope] ◄─── V'
@.8 = 'the lovers ◄─── VI'
@.9 = 'the chariot ◄─── VII'
@.10= 'justice ◄─── VIII'
@.11= 'the hermit ◄─── IX'
@.12= 'fortune [the wheel of] ◄─── X'
@.13= 'strength ◄─── XI'
@.14= 'the hanging man ◄─── XII'
@.15= 'death [often unlabeled] ◄─── XIII'
@.16= 'temperance ◄─── XIV'
@.17= 'the devil ◄─── XV'
@.18= 'lightning [the tower] ◄─── XVI'
@.18= 'the stars ◄─── XVII'
@.20= 'the moon ◄─── XVIII'
@.21= 'the sun ◄─── XIX'
@.22= 'judgment ◄─── XX'
@.23= 'the world ◄─── XXI'
@.24= 'the fool [often unnumbered] ◄─── XXII'
do #= 1 until @.#==''; end; #= #-1 /*find how many entries in the array. */
return /* [↑] adjust for DO loop advancement.*/
/*──────────────────────────────────────────────────────────────────────────────────────*/
show: w= length(#); do j=1 for # /*#: is the number of items in @. */
say 'element' right(j, w) arg(1)":" @.j
end /*j*/ /* ↑ */
return /* └─────max width of any line.*/
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