按值和键排序哈希(按此顺序)

Question

我正在寻找一种很好的方法来首先按值排序Perl,然后按键排序.

例:

 my %userids = (
  williams => "Marketing",
  smith    => "Research",
  johnson  => "Research",
  jones    => "Marketing",
  brown    => "Marketing",
  davis    => "Research"
);

输出:

Marketing: brown
Marketing: jones
Marketing: williams
Research: davis
Research: johnson
Research: smith

请注意,值是第一个排序级别.第二个排序级别是关键.知道如何以优雅和高性能的方式做到这一点吗？谢谢!

Answer 1

很好的参考:http://www.misc-perl-info.com/perl-sort.html#shv

#!/usr/bin/perl

my %userids = (
    williams => "Marketing",
    smith    => "Research",
    johnson  => "Research",
    jones    => "Marketing",
    brown    => "Marketing",
    davis    => "Research"
);

foreach (sort { ($userids{$a} cmp $userids{$b}) || ($a cmp $b) } keys %userids) 
{
    print "$_: $userids{$_}\n";
}

Answer 2

我想补充一点,用于\L sequence排序.

从Perlfaq4:我如何排序哈希(可选择按值而不是键)？

为了使我们的报表顺序不区分大小写,我们使用\L sequence双引号字符串将所有内容都设置为小写.sort()然后该块比较较低的值以确定放置键的顺序.

foreach (sort { $userids{$a} cmp $userids{$b} or "\L$a" cmp "\L$b" )  {
    print "$_: $userids{$_}\n"; 
} 

输出:

brown: Marketing
jones: Marketing
williams: Marketing
davis: Research
Johnson: Research # here 'J'ohnson, J is in uppercase(taking assumption), come as fifth record
smith: Research

2.

foreach (sort { $userids{$a} cmp $userids{$b} or $a cmp $b )  {
    print "$_: $userids{$_}\n"; 
}

输出:

brown: Marketing
jones: Marketing
williams: Marketing
Johnson: Research # here it shifted to fourth record
davis: Research
smith: Research