42 lines
3.6 KiB
Rexx
42 lines
3.6 KiB
Rexx
/*REXX pgm solves the continuous burglar's knapsack problem; items with weight and value*/
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@.= /*═══════ name weight value ══════*/
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@.1 = 'flitch 4 30 '
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@.2 = 'beef 3.8 36 '
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@.3 = 'pork 5.4 43 '
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@.4 = 'greaves 2.4 45 '
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@.5 = 'brawn 2.5 56 '
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@.6 = 'welt 3.7 67 '
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@.7 = 'ham 3.6 90 '
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@.8 = 'salami 3 95 '
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@.9 = 'sausage 5.9 98 '
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parse arg maxW d . /*get possible arguments from the C.L. */
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if maxW=='' | maxW=="," then maxW=15 /*the burglar's knapsack maximum weight*/
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if d=='' | d=="," then d= 3 /*# decimal digits shown with FORMAT. */
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wL=d+length('weight'); nL=d+length("total weight"); vL=d+length('value') /*lengths*/
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totW=0; totV=0 /* [↓] assign item to separate lists. */
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do #=1 while @.#\==''; parse var @.# n.# w.# v.# .; end; #=#-1
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call show 'unsorted item list' /*display the header and the @ list.*/
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call sortD /*invoke descemdomg sort for: n. w. v.*/
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call hdr "burglar's knapsack contents"
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do j=1 for # while totW<maxW; f=1 /*process the items. */
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if totW+w.j>=maxW then f=(maxW-totW)/w.j /*calculate fraction. */
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totW=totW+w.j*f; totV=totV+v.j*f /*add it ───► totals. */
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call syf left(word('{all}',1+(f\==1)),5) n.j, w.j*f, v.j*f
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end /*j*/ /* [↑] display item, maybe with {all} */
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call sep; say /* [↓] $ suppresses trailing zeroes.*/
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call sy left('total weight', nL, "─"), $(format(totW,,d))
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call sy left('total value', nL, "─"), , $(format(totV,,d))
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exit /*stick a fork in it, we're all done. */
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/*──────────────────────────────────────────────────────────────────────────────────────*/
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sortD: do s=2 to #; a=n.s; !=w.s; u=v.s /* [↓] this is a descending sort. */
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do k=s-1 by -1 to 1 while v.k/w.k<u/!; ?=k+1; n.?=n.k; w.?=w.k; v.?=v.k; end
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?=k+1; n.?=a; w.?=!; v.?=u
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end /*s*/; return /* ↑↑↑ algorithm is OK for small arrays*/
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/*──────────────────────────────────────────────────────────────────────────────────────*/
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hdr: say; say; say center(arg(1),50,'─'); say; call title; call sep; return
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sep: call sy copies('═', nL), copies("═", wL), copies('═', vL); return
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show: call hdr arg(1); do j=1 for #; call syf n.j, w.j, v.j; end; return
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sy: say left('',9) left(arg(1),nL) right(arg(2),wL) right(arg(3),vL); return
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syf: call sy arg(1), $(format(arg(2), , d)), $(format(arg(3), , d)); return
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title: call sy center('item',nL), center("weight", wL), center('value', vL); return
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$: parse arg x;if pos(.,x)>1 then x=left(strip(strip(x,'T',0),,.),length(x)); return x
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