make nextPermutation faster
#497
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LGTM. Extra strictness won't cause any problems since I make simple benchmark and this change reduced execution time 5× and allocations 9×. Most gains seems to come from @toyboot4e do you plan any more optimizations? |
Contributor
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In our private conversation on Twitter, oh, X (in Japanese), I have suggested some optimizations to him/her, and (s)he suggested that I take this over. I'm submitting superceding PR. |
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Thank you! Closing in favor of #498. |
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This PR makes
nextPermutationlike 10 times faster, resolving theTODOfrom 2014:Let's do it!
Edit:
stToPrim(suggested by @gksato) makes it even faster. WithstToPrim, the bangs are not needed for the speed, but I preferred explicit strict evaluation.If anyone is interested, here's my AtCoder submissions for a simple speed comparsion:
GM.nextPermutation: time limit exceedGM.nextPermutationwith tuples unboxed: accepted (281 ms in the worst case)GM.nextPermutationwithstToPrimand with tuples unboxed: accepted (231 ms in the worst case)