对嵌套散列的散列键进行排序 [英] Sort hash keys of nested hash

问题描述

在perl中，我有一个如下所示的哈希：

  $ hash {key1}  - > {a } = 1; 
 $ hash {key1}  - > {b} = 3; 
 
 $ hash {key2}  - > {a} = 4; 
 $ hash {key2}  - > {b} = 7; 
 
 $ hash {key3}  - > {a} = 2; 
 $ hash {key3}  - > {b} = 5; 
  

如何通过键 a的值来排序此散列的键。例如，按键 a 的值按数字升序对上述散列进行排序将给出：key1，key3，key2。

解决方案

perl没有排序哈希的概念，您必须在foreach循环中排序您的键：

 ＃！/ usr / bin / perl -W 
 use strict; 
 
 my％hash =（）; 
 
 $ hash {key1}  - > {a} = 1; 
 $ hash {key1}  - > {b} = 3; 
 
 $ hash {key2}  - > {a} = 4; 
 $ hash {key2}  - > {b} = 7; 
 
 $ hash {key3}  - > {a} = 2; 
 $ hash {key3}  - > {b} = 5; 
 
 print$ _\\\
foreach sort {$ hash {$ a}  - > {a}< => $ hash {$ b}  - > {a}}键％hash; 
  

或者，您可以将 sort的结果在数组中循环。

In perl, I have a hash that looks like the following:

   $hash{key1}->{a} = 1;
   $hash{key1}->{b} = 3;

   $hash{key2}->{a} = 4;
   $hash{key2}->{b} = 7;

   $hash{key3}->{a} = 2;
   $hash{key3}->{b} = 5;

How can I sort the keys of this hash by the value of key a. For instance, sorting the above hash in numerical ascending order by the values of key a would give: key1,key3,key2.

解决方案

perl has no notion of a sorted hash, you'll have to "sort" your keys in a foreach loop:

#!/usr/bin/perl -W
use strict;

my %hash = ();

$hash{key1}->{a} = 1;
$hash{key1}->{b} = 3;

$hash{key2}->{a} = 4;
$hash{key2}->{b} = 7;

$hash{key3}->{a} = 2;
$hash{key3}->{b} = 5;

print "$_\n" foreach sort {$hash{$a}->{a} <=> $hash{$b}->{a}} keys %hash;

Alternatively, you can put the result of the sort in an array and loop on this array.

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