Combinations: Difference between revisions

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→‎{{header|Phix}}: added syntax colouring the hard way
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m (→‎{{header|Phix}}: added syntax colouring the hard way)
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=={{header|Phix}}==
It does not get much simpler or easier than this. See [[Sudoku#Phix|Sudoku]] for a practical application of this algorithm
<!--<lang Phix>(phixonline)-->
<lang Phix>procedure comb(integer pool, needed, done=0, sequence chosen={})
<span style="color: #008080;">with</span> <span style="color: #008080;">javascript_semantics</span>
if needed=0 then -- got a full set
<span style="color: #008080;">procedure</span> <span style="color: #000000;">comb</span><span style="color: #0000FF;">(</span><span style="color: #004080;">integer</span> <span style="color: #000000;">pool</span><span style="color: #0000FF;">,</span> <span style="color: #000000;">needed</span><span style="color: #0000FF;">,</span> <span style="color: #000000;">done</span><span style="color: #0000FF;">=</span><span style="color: #000000;">0</span><span style="color: #0000FF;">,</span> <span style="color: #004080;">sequence</span> <span style="color: #000000;">chosen</span><span style="color: #0000FF;">={})</span>
?chosen -- (or use a routine_id, result arg, or whatever)
<span style="color: #008080;">if</span> <span style="color: #000000;">needed</span><span style="color: #0000FF;">=</span><span style="color: #000000;">0</span> <span style="color: #008080;">then</span> <span style="color: #000080;font-style:italic;">-- got a full set</span>
return
<span style="color: #0000FF;">?</span><span style="color: #000000;">chosen</span> <span style="color: #000080;font-style:italic;">-- (or use a routine_id, result arg, or whatever)</span>
end if
<span style="color: #008080;">return</span>
if done+needed>pool then return end if -- cannot fulfil
<span style="color: #008080;">end</span> <span style="color: #008080;">if</span>
-- get all combinations with and without the next item:
<span style="color: #008080;">if</span> <span style="color: #000000;">done</span><span style="color: #0000FF;">+</span><span style="color: #000000;">needed</span><span style="color: #0000FF;">></span><span style="color: #000000;">pool</span> <span style="color: #008080;">then</span> <span style="color: #008080;">return</span> <span style="color: #008080;">end</span> <span style="color: #008080;">if</span> <span style="color: #000080;font-style:italic;">-- cannot fulfil
done += 1
-- get all combinations with and without the next item:</span>
comb(pool,needed-1,done,append(chosen,done))
<span style="color: #000000;">done</span> <span style="color: #0000FF;">+=</span> <span style="color: #000000;">1</span>
comb(pool,needed,done,chosen)
<span style="color: #000000;">comb</span><span style="color: #0000FF;">(</span><span style="color: #000000;">pool</span><span style="color: #0000FF;">,</span><span style="color: #000000;">needed</span><span style="color: #0000FF;">-</span><span style="color: #000000;">1</span><span style="color: #0000FF;">,</span><span style="color: #000000;">done</span><span style="color: #0000FF;">,</span><span style="color: #7060A8;">append</span><span style="color: #0000FF;">(</span><span style="color: #7060A8;">deep_copy</span><span style="color: #0000FF;">(</span><span style="color: #000000;">chosen</span><span style="color: #0000FF;">),</span><span style="color: #000000;">done</span><span style="color: #0000FF;">))</span>
end procedure
<span style="color: #000000;">comb</span><span style="color: #0000FF;">(</span><span style="color: #000000;">pool</span><span style="color: #0000FF;">,</span><span style="color: #000000;">needed</span><span style="color: #0000FF;">,</span><span style="color: #000000;">done</span><span style="color: #0000FF;">,</span><span style="color: #000000;">chosen</span><span style="color: #0000FF;">)</span>
<span style="color: #008080;">end</span> <span style="color: #008080;">procedure</span>
comb(5,3)</lang>
<span style="color: #000000;">comb</span><span style="color: #0000FF;">(</span><span style="color: #000000;">5</span><span style="color: #0000FF;">,</span><span style="color: #000000;">3</span><span style="color: #0000FF;">)</span>
<!--</lang>-->
{{out}}
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