Sorting algorithms/Heapsort: Difference between revisions

=={{header|REXX}}==

<lang rexx>

/*REXX program sorts an array using the heapsort method. */

call gen@ /*generate array elements. */

call show@ 'before sort' /*show before array elements*/

call heapSort highItem /*invoke the heap sort. */

call show@ ' after sort' /*show after array elements*/

exit

/*─────────────────────────────────────HEAPSORT subroutine─────────*/

heapSort: procedure expose @.; parse arg n

do j=n%2 by -1 to 1

call shuffle j,n

end

do n=n by -1 to 2

_=@.1; @.1=@.n; @.n=_; call shuffle 1,n

end

return

/*─────────────────────────────────────SHUFFLE subroutine──────────*/

shuffle: procedure expose @.; parse arg i,n; _=@.i

do while i+i<=n

j=i+i; k=j+1

if k<=n & @.k>@.j then j=k

if _>=@.j then leave

@.i=@.j; i=j

end

@.i=_

return

/*─────────────────────────────────────GEN@ subroutine─────────────*/

gen@: @.='' /*assign default value. */

@.1 ='---letters of the modern Greek Alphabet---'

@.2 ='=========================================='

@.3 ='alpha'

@.4 ='beta'

@.5 ='gamma'

@.6 ='delta'

@.7 ='epsilon'

@.8 ='zeta'

@.9 ='eta'

@.10='theta'

@.11='iota'

@.12='kappa'

@.13='lambda'

@.14='mu'

@.15='nu'

@.16='xi'

@.17='omicron'

@.18='pi'

@.19='rho'

@.20='sigma'

@.21='tau'

@.22='upsilon'

@.23='phi'

@.24='chi'

@.25='psi'

@.26='omega'

do highItem=1 while @.highItem\=='' /*find how many entries. */

end

highItem=highItem-1 /*adjust highItem slightly. */

return

/*─────────────────────────────────────SHOW@ subroutine────────────*/

show@: widthH=length(highItem) /*maximum widht of any line.*/

do j=1 for highItem

say 'element' right(j,widthH) arg(1)':' @.j

end

say copies('─',80) /*show a seperator line. */

return

</lang>

Output:

<pre style="height:30ex;overflow:scroll">

element 1 before sort: ---letters of the modern Greek Alphabet---

element 2 before sort: ==========================================

element 3 before sort: alpha

element 4 before sort: beta

element 5 before sort: gamma

element 6 before sort: delta

element 7 before sort: epsilon

element 8 before sort: zeta

element 9 before sort: eta

element 10 before sort: theta

element 11 before sort: iota

element 12 before sort: kappa

element 13 before sort: lambda

element 14 before sort: mu

element 15 before sort: nu

element 16 before sort: xi

element 17 before sort: omicron

element 18 before sort: pi

element 19 before sort: rho

element 20 before sort: sigma

element 21 before sort: tau

element 22 before sort: upsilon

element 23 before sort: phi

element 24 before sort: chi

element 25 before sort: psi

element 26 before sort: omega

────────────────────────────────────────────────────────────────────────────────

element 1 after sort: eta

element 2 after sort: ==========================================

element 3 after sort: chi

element 4 after sort: beta

element 5 after sort: delta

element 6 after sort: ---letters of the modern Greek Alphabet---

element 7 after sort: theta

element 8 after sort: iota

element 9 after sort: omicron

element 10 after sort: lambda

element 11 after sort: omega

element 12 after sort: kappa

element 13 after sort: nu

element 14 after sort: mu

element 15 after sort: epsilon

element 16 after sort: alpha

element 17 after sort: phi

element 18 after sort: pi

element 19 after sort: psi

element 20 after sort: rho

element 21 after sort: sigma

element 22 after sort: tau

element 23 after sort: gamma

element 24 after sort: upsilon

element 25 after sort: xi

element 26 after sort: zeta

────────────────────────────────────────────────────────────────────────────────

</pre>