Thank you all for your replies.
I tested the 5 solutions with the benchmark module, and the splice one is the fastest: Benchmark: timing 999999 iterations of each, grep, hash, keep, splice... each: 5 wallclock secs ( 5.07 usr + 0.00 sys = 5.07 CPU) @ 197238.46/s (n=999999) grep: 5 wallclock secs ( 4.96 usr + 0.00 sys = 4.96 CPU) @ 201612.70/s (n=999999) hash: 6 wallclock secs ( 5.37 usr + 0.00 sys = 5.37 CPU) @ 186219.55/s (n=999999) keep: 2 wallclock secs ( 1.68 usr + 0.00 sys = 1.68 CPU) @ 595237.50/s (n=999999) splice: 1 wallclock secs ( 1.40 usr + 0.00 sys = 1.40 CPU) @ 714285.00/s (n=999999) The hash one, which was my first solution is the slowest one. :-( code and results: https://pastebin.com/FYdJzVzu Thanks all. Regards, David Santiago On Wed, 12 Apr 2017 16:50:49 -0400 Uri Guttman <u...@stemsystems.com> wrote: > On 04/12/2017 04:38 PM, Shlomi Fish wrote: > > Hi Uri! > > > > Some notes. > > > > On Wed, 12 Apr 2017 15:19:33 -0400 > > Uri Guttman <u...@stemsystems.com> wrote: > > > >> On 04/12/2017 03:00 PM, David Emanuel da Costa Santiago wrote: > >>> Hello! > >>> > >>> What's the best way to delete multiple indices from an array? > >>> > >>> i'm doing: > >>> > >>> --------------- > >>> my @array=qw/zero one two three four five six seven eight nine > >>> ten/; > >>> > >>> my @indicesToDelete = (2,4,6,7); > >> if you have the indexes to keep, this would be a simple slice: > >> > >> my @keep_indexes = ( 0, 1, 3, 5, 8,9 10 ); > >> @array = @array{ @keep_indexes } ; > >> > > it should be «@array = @array[ @keep_indexes ] ;» instead. With > > curly braces it's a hash slice. > > > >> so one idea is to make that list of kept indexes from the list of > >> indexes to delete: > >> > >> my %keep_hash ; > >> @keep_hash{ 0 .. 10 } = () ; # no need for any values so this save > >> space delete @keep_hash{ @keep_indexes } ; > >> @array = @array{ keys %keep_hash } ; > > 1. again - square brackets instead of curly braces. > yes, i missed that. > > > > 2. You should sort the keys numerically using sort { $a <=> $b }. > i don't sort the indexes. that was some other code. > > > > 3. Better use « keys@array» or in older perls «0 .. $#array» to > > avoid hard coding the values and magic constants. > again, that wasn't my code. > > > ============ > > > > some other ways I can think of doing it: > > > > 1. > > > > my %blacklist; > > @blacklist{@remove} = (); > > @array = @array[grep {!exists $blacklist{$_} } keys@array]; > > > > 2. > > > > my @new; > > while (my ($i, $v) = each@array) > > { > > if (@remove and $i == $remove[0]) > > { > > shift@remove; > > } > > else > > { > > push @new, $v; > > } > > } > > @array = @new > that is a much slower version of your grep solution. > > uri > -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
