按值和鍵排序哈希（按此順序）

Question

我正在尋找一種很好的方法，首先按值排序哈希值，然後再按鍵。

實施例：

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

輸出：

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

請注意，值是第一個排序級別。第二個分類等級是密鑰。任何想法如何以優雅和高性能的方式做到這一點？謝謝！

Answer 1

很好的參考：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

我想補充一點，在分揀使用\L sequence。

從Perlfaq4：如何對散列進行排序（可選擇使用值而不是鍵）？

爲了使我們的報表順序不區分大小寫，我們在雙引號字符串中使用\L sequence以使所有內容都爲小寫。 sort()塊然後比較小寫的值以確定按照何種順序放置鍵。

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

輸出：

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"; 
} 

輸出：

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