perl – 根据插入顺序迭代哈希?
发布时间:2020-12-15 22:01:42 所属栏目:大数据 来源:网络整理
导读:不想对条目进行排序. 使用它也不会保留顺序 foreach my $val (keys %hash) { ... } 解决方法 默认情况下,Perl 5中的哈希是无序的.您可以使用 tie 和 Tie::IxHash 来覆盖此行为.不过要警告,有一个表现打击和其他考虑(例如,这个订单不会保留在副本中). #!/usr/
不想对条目进行排序.
使用它也不会保留顺序 foreach my $val (keys %hash) { ... } 解决方法
默认情况下,Perl 5中的哈希是无序的.您可以使用
tie 和
Tie::IxHash 来覆盖此行为.不过要警告,有一个表现打击和其他考虑(例如,这个订单不会保留在副本中).
#!/usr/bin/perl use strict; use warnings; use Tie::IxHash; tie my %hash,"Tie::IxHash" or die "could not tie %hash"; $hash{one} = 1; $hash{two} = 2; $hash{three} = 3; for my $k (keys %hash) { print "$k $hash{$k}n"; } 更好的选择可能是使用数组或散列哈希: #!/usr/bin/perl use strict; use warnings; my %hash; $hash{one} = { data => 1,order => 1 }; $hash{three} = { data => 3,order => 2 }; $hash{two} = { data => 2,order => 3 }; for my $k (sort { $hash{$a}{order} <=> $hash{$b}{order} } keys %hash) { print "$k $hash{$k}{data}n"; } 至于表现,以下是一个基准的结果: IndexedOO: a,b,c,d,e,f HashOrdered: a,f IxHashOO: a,f hash: f,a,d hoh_pis: a,f IxHash: a,f hoh: a,f Indexed: a,f Rate IxHash hoh Indexed IxHashOO IndexedOO hoh_pis HashOrdered hash IxHash 261/s -- -18% -26% -48% -54% -57% -66% -80% hoh 316/s 21% -- -10% -37% -44% -48% -59% -75% Indexed 353/s 35% 12% -- -29% -38% -42% -55% -72% IxHashOO 499/s 91% 58% 41% -- -12% -18% -36% -61% IndexedOO 569/s 118% 80% 61% 14% -- -7% -27% -56% hoh_pis 611/s 134% 93% 73% 22% 7% -- -21% -52% HashOrdered 778/s 198% 146% 120% 56% 37% 27% -- -39% hash 1279/s 391% 305% 262% 156% 125% 109% 64% -- 从这里我们可以看到,如果您不需要使用Hash :: Ordered就可以像普通哈希(即绑定的哈希)那样运行. 这是基准: #!/usr/bin/perl use strict; use warnings; use Tie::IxHash; use Tie::Hash::Indexed; use Hash::Ordered; use Benchmark; #this is O(n) instead of O(n log n) or worse sub perfect_insert_sort { my $h = shift; my @k; for my $k (keys %$h) { $k[$h->{$k}{order}] = $k; } return @k; } my @keys = qw/a b c d e f/; my %subs = ( hash => sub { my $i; my %h = map { $_ => $i++ } @keys; return join ",",keys %h; },hoh => sub { my $i; my $order; my %h = map { $_ => { data => $i++,order => $order++ } } @keys; return join ",sort { $h{$a}{order} <=> $h{$b}{order} } keys %h; },hoh_pis => sub { my $i; my $order; my %h = map { $_ => { data => $i++,perfect_insert_sort %h; },IxHash => sub { my $i; tie my %h,"Tie::IxHash"; %h = map { $_ => $i++ } @keys; return join ",Indexed => sub { my $i; tie my %h,"Tie::Hash::Indexed"; %h = map { $_ => $i++ } @keys; return join ",IxHashOO => sub { my $i; my $o = tie my %h,"Tie::IxHash",map { $_ => $i++ } @keys; return join ",$o->Keys; },IndexedOO => sub { my $i; my $o = tie my %h,"Tie::Hash::Indexed",map { $_ => $i++ } @keys; my @k = my $k = $o->FIRSTKEY; while ($k = $o->NEXTKEY($k)) { push @k,$k; } return join ",@k; },HashOrdered => sub { my $i; my $oh = Hash::Ordered->new( map { $_ => $i++ } @keys ); return join ",$oh->keys; },); for my $sub (keys %subs) { print "$sub: ",$subs{$sub}(),"n"; } @keys = 1 .. 1_000; Benchmark::cmpthese -2,%subs; (编辑:李大同) 【声明】本站内容均来自网络,其相关言论仅代表作者个人观点,不代表本站立场。若无意侵犯到您的权利,请及时与联系站长删除相关内容! |