Perl通过哈希中的值对哈希进行排序 [英] Perl sorting hash by values in the hash

问题描述

我认为我有正确的想法，但有一些语法/约定的东西我搞乱了，因为我得到错误全局符号％timeHash需要明确的包名称。

$ p
$ b

  foreach $ key（sort hashValueDescendingNum（keys（％timeHash）））{
 print \t $ key \t\t $ timeHash {$ key} \\\
; 
} 
 
 
 
 sub hashValueDescendingNum {
 my $ hash = shift; 
 $ hash {$ b}< => $哈希{$ a}的; 
} 
  

解决方案

内联

  foreach my $ key（sort {$ timeHash {$ b}< => $ timeHash {$ a}} keys％timeHash）{
打印\t $ key\t\t $ timeHash {$ key} \\\
; 
 
  

使用自定义排序功能的方式不会奏效，因为那么你的子将需要访问原始散列。

  foreach my $ key（sort hashValueDescendingNum（keys（％timeHash）） ）{
 print\t $ key \t\t $ timeHash {$ key} \\\
; 
} 
 
 sub hashValueDescendingNum {
 $ timeHash {$ b}< => $ timeHash {$ a}的; ＃Ew。 
} 
  

相反，您可以进一步抽象：

  foreach my $ key（sortedHashKeysByValueDescending（％timeHash））{
 print\ t $ key \t\t $ timeHash {$ key} \\\
; 
} 
 
 sub sortedHashKeysByValueDescending {
 my％hash = @_; 
 my @keys = sort {$ hash {$ b}< => $ hash {$ a}}键％hash; 
返回@keys; 
} 
  

代码效率不高，因为它传递％hash，但引用会更好：

  foreach my $ key（sortedHashKeysByValueDescending（\％timeHash））{
 print\t $ key\t\t $ timeHash {$ key} \\\
; 
} 
 
 sub sortedHashKeysByValueDescending {
 my $ hash = shift; 
返回排序{$ hash-> {$ b}< => $ hash-> {$ a}}键％$ hash; 
} 
  

I think I have the right idea but there's some syntax/convention thing I'm messing up, because I get the error "Global symbol %timeHash requires explicit package name".

Code:

foreach $key (sort hashValueDescendingNum (keys(%timeHash))) {
   print "\t$key\t\t $timeHash{$key}\n";
}



sub hashValueDescendingNum {
   my $hash = shift;
   $hash{$b} <=> $hash{$a};
}

解决方案

Inline

foreach my $key (sort { $timeHash{$b} <=> $timeHash{$a} } keys %timeHash) {
   print "\t$key\t\t $timeHash{$key}\n";
}

Using a custom sort function the way you are trying to will not work well, because then your sub would need to access the original hash.

foreach my $key (sort hashValueDescendingNum (keys(%timeHash))) {
    print "\t$key\t\t $timeHash{$key}\n";
}

sub hashValueDescendingNum {
   $timeHash{$b} <=> $timeHash{$a}; # Ew.
}

Instead you can abstract it further:

foreach my $key (sortedHashKeysByValueDescending(%timeHash)) {
    print "\t$key\t\t $timeHash{$key}\n";
}

sub sortedHashKeysByValueDescending {
  my %hash = @_;
  my @keys = sort { $hash{$b} <=> $hash{$a} } keys %hash;
  return @keys;
}

The code is not efficient because it passes around the %hash though, references would be better:

foreach my $key (sortedHashKeysByValueDescending(\%timeHash)) {
    print "\t$key\t\t $timeHash{$key}\n";
}

sub sortedHashKeysByValueDescending {
  my $hash = shift;
  return sort { $hash->{$b} <=> $hash->{$a} } keys %$hash;
}

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