按值对哈希排序

Question

这不是我填充哈希的方式。为了更容易阅读，这里是它的内容，键在一个固定长度的字符串上：

my %country_hash = (
  "001 Sample Name   New Zealand" => "NEW ZEALAND",
  "002 Samp2 Nam2    Zimbabwe   " => "ZIMBABWE",
  "003 SSS NNN       Australia  " => "AUSTRALIA",
  "004 John Sample   Philippines" => "PHILIPPINES,
);

我想根据值获取排序的键。所以我的期望：

"003 SSS NNN       Australia  "
"001 Sample Name   New Zealand"
"004 John Sample   Philippines"
"002 Samp2 Nam2    Zimbabwe   "

我做了什么：

foreach my $line( sort {$country_hash{$a} <=> $country_hash{$b} or $a cmp $b} keys %country_hash ){
  print "$line\n";
}

还; （我怀疑这会排序，但无论如何）

my @sorted = sort { $country_hash{$a} <=> $country_hash{$b} } keys %country_hash;
foreach my $line(@sorted){
  print "$line\n";
}

他们都没有正确排序。我希望有人可以提供帮助。

Answer 1

如果您使用了warnings，您会被告知这<=>是错误的运算符；它用于数值比较。使用cmp字符串比较来代替。请参阅排序。

use warnings;
use strict;

my %country_hash = (
  "001 Sample Name   New Zealand" => "NEW ZEALAND",
  "002 Samp2 Nam2    Zimbabwe   " => "ZIMBABWE",
  "003 SSS NNN       Australia  " => "AUSTRALIA",
  "004 John Sample   Philippines" => "PHILIPPINES",
);

my @sorted = sort { $country_hash{$a} cmp $country_hash{$b} } keys %country_hash;
foreach my $line(@sorted){
    print "$line\n";
}

这打印：

003 SSS NNN       Australia  
001 Sample Name   New Zealand
004 John Sample   Philippines
002 Samp2 Nam2    Zimbabwe   

这也有效（没有额外的数组）：

foreach my $line (sort {$country_hash{$a} cmp $country_hash{$b}} keys %country_hash) {
    print "$line\n";
}