基于Perl中哈希值排序的简单方法 [英] The simple way to sort based on values in a hash in perl

问题描述

通常可以根据键进行排序，然后迭代哈希，如下所示:

Normally sorting based on keys and then iterating a hash can be done as following:

for $k (sort (keys %h)) {
  print $k, $h{$k};
}

但是如何基于值进行排序，然后遍历哈希呢?我可以考虑通过交换键和值对来创建新的哈希.但是还有其他更聪明的方法吗?

But how to do the sorting based on values and then iterate through the hash? I can think of creating a new hash by swapping the key and value pairs. But is there any more clever way of doing this?

非常感谢.

推荐答案

如果希望排序比较器不是cmp，则可以提供代码块或子例程作为sort的第一个参数.有关更多详细信息，请参见文档.

If you want the sort comparator to be something other than cmp, you can supply a code block or a subroutine as the first parameter to sort. See the documentation for more details.

my %h = (
    aaaa => 'z',
    bbb  => 'x',
    c    => 'y',
);

# Sort on hash values.
for my $k (sort {$h{$a} cmp $h{$b}} keys %h) {
    print $k, "\n";   # bbb c aaaa
}

# Sort using a named subroutine.
for my $k (sort by_length keys %h) {
    print $k, "\n";   # c bbb aaaa
}

sub by_length {
    length($a) <=> length($b);
}

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