Sorting algorithms/Selection sort: Difference between revisions

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=={{header|REXX}}==

<lang rexx>/*REXX program sorts a stemmed array using the selection─sort algorithm. */

~~@.=;~~ ~~@.1~~ = ~~'---The~~ ~~seven~~ ~~hills~~ of ~~Rome~~:~~---'~~

call init /*assign some values to an array: @. */

@.2 = '=============================='; @.6 = 'Virminal'

@.3 = 'Caelian' ; @.7 = 'Esquiline'

@.4 = 'Palatine' ; @.8 = 'Quirinal'

@.5 = 'Capitoline' ; @.9 = 'Aventine'

do #=1 until @.#==''; end /*find the number of items in the array*/

~~# = # - 1~~ /*adjust # (because of DO index). */

call show 'before sort' /*show the before array elements. */

say copies('▒', 65) /*show a nice separator line (fence). */

call selectionSort # /*invoke selection sort (and # items). */

call show ' after sort' /*show the after array elements. */

exit /*stick a fork in it, we're ~~a;;~~ done. */

exit /*stick a fork in it, we're all done. */

/*──────────────────────────────────────────────────────────────────────────────────────*/

init: @.=; @.1 = '---The seven hills of Rome:---'

@.2 = '=============================='; @.6 = 'Virminal'

@.3 = 'Caelian' ; @.7 = 'Esquiline'

@.4 = 'Palatine' ; @.8 = 'Quirinal'

@.5 = 'Capitoline' ; @.9 = 'Aventine'

do #=1 until @.#==''; end /*find the number of items in the array*/

#= #-1; return /*adjust # (because of DO index). */

/*──────────────────────────────────────────────────────────────────────────────────────*/

selectionSort: procedure expose @.; parse arg n

do j=1 for n-1; _= @.j; p= j

do k=j+1 to n; if @.k>=_ then iterate

_= @.k; p= k /*this item is out─of─order, swap later*/

end /*k*/

if p==j then iterate /*if the same, the order of items is OK*/

_= @.j; @.j= @.p; @.p= _ /*swap 2 items that're out─of─sequence.*/

end /*j*/

return

/*──────────────────────────────────────────────────────────────────────────────────────*/