在 Perl 中对散列进行排序

原文:https://www.geeksforgeeks.org/sorting-hash-in-perl/

先决条件: Perl | Hashes

一组键/值对被称为哈希。哈希结构中的每个键都是唯一的，并且是类型字符串。与这些键相关联的值是标量。这些值可以是数字、字符串或引用。哈希是用我的关键字声明的。让我们考虑一个例子来理解散列排序的概念。

例子:考虑一个班级学生名字和他们平均分数的散列。这里，学生的名字是关键，他们的平均成绩是数值。使用keys 函数返回的学生姓名上的 foreach 循环打印该散列。

# Perl program to demonstrate 
# the concept of hash
use strict;
use warnings;
use 5.010;

# Creating a hash of studentnames 
# and their average score
my %studentnames = (
Martha => 14,
Vivek => 27,
Earl => 31,
Marty => 16.5,
Jason => 25.2,
Socrates => 29.5,
Uri => 19.6,
Nitin => 30,
Plato => 39,
);

# displaying the keys and values of Hash
# using the foreach loop and keys function 
# output may be different each 
# time when you run the code
foreach my $name (keys %studentnames) {

    # printing the keys and values of hash
    printf "%-8s %s\n", $name, $studentnames{$name};
}

输出:

Marty    16.5
Jason    25.2
Plato    39
Vivek    27
Socrates 29.5
Martha   14
Earl     31
Uri      19.6
Nitin    30

注意:输出可能包含任何随机顺序，具体取决于系统和 Perl 的版本。

哈希可以通过如下多种方式排序:

• 根据哈希键的 ASCII 值对哈希进行排序:一般来说，排序是基于 ASCII 表的。这意味着排序会将所有大写字母放在所有小写字母的前面。这是排序的默认行为。上面的示例代码是根据其键的 ASCII 值排序的。

• Sorting the Hash according to the alphabetical order of its keys: Here, the keys are sorted alphabetically.

  示例:

  ```perl

  Perl program to demonstrate

  sorting of the hash according

  alphabetical order of its keys

  use strict; use warnings; use 5.010;

  Creating a hash of studentnames

  and their average score

  my %studentnames = ( Martha => 14, Vivek => 27, Earl => 31, Marty => 16.5, Jason => 25.2, Socrates => 29.5, Uri => 19.6, Nitin => 30, Plato => 39, );

  sorting the hash according

  alphabetical order of its keys

  foreach my $name (sort {lc $a cmp lc $b} keys %studentnames)  {     printf "%-8s %s\n", $name, \(studentnames{\)name}; } ```

  输出:

  ```perl Earl 31 Jason 25.2 Martha 14 Marty 16.5 Nitin 30 Plato 39 Socrates 29.5 Uri 19.6 Vivek 27

  ```

• Sorting according to the values of Hash: You can also sort the hash according to the values of hash as follows:

  示例 1: 根据 ASCII 表对哈希值进行排序。

  ```perl

  Perl program to demonstrate

  sorting of the hash according

  to the values of Hash

  use strict; use warnings; use 5.010;

  Creating a hash of studentnames

  and their average score

  my %studentnames = ( Martha => 14, Vivek => 27, Earl => 31, Marty => 16.5, Jason => 25.2, Socrates => 29.5, Uri => 19.6, Nitin => 30, Plato => 39, );

  sorting of the hash according

  to ASCII code of values of Hash

  foreach my $name (sort values %studentnames)  {     say $name; } ```

  输出:

  ```perl 14 16.5 19.6 25.2 27 29.5 30 31 39

  ```

  例 2: 根据哈希值的数值排序如下:

  ```perl

  Perl program to demonstrate

  sorting of the hash according

  to the values of Hash

  use strict; use warnings; use 5.010;

  Creating a hash of studentnames

  and their average score

  my %studentnames = ( Martha => 14, Vivek => 27, Earl => 31, Marty => 16.5, Jason => 25.2, Socrates => 29.5, Uri => 19.6, Nitin => 30, Plato => 39, );

  sorting of the hash according

  to the numerical value of

  Values of hash

  foreach my \(name (sort {\)a<=>$b} values %studentnames)  {     say $name; } ```

  输出:

  ```perl 14 16.5 19.6 25.2 27 29.5 30 31 39

  ```

• Sort the keys of the hash according to the values: You can also sort the keys of hash according to the given values.

  示例 1: 在下面的程序中，< = >被称为宇宙飞船操作员。如果您反复运行代码，那么您可以注意到输出中的差异。有时你会在之前找到柏拉图，反之亦然。

  ```perl

  Perl program to demonstrate the

  Sorting of keys of the hash

  according to the values

  use strict; use warnings; use 5.010;

  Creating a hash of studentnames

  and their average score

  my %studentnames = ( Martha => 14, Vivek => 27, Earl => 31, Marty => 16.5, Jason => 25.2, Socrates => 29.5, Uri => 19.6, Nitin => 45, Plato => 45, );

  Sort the keys of the hash

  according to the values

  Here $a and $b are the

  placeholder variable of sort

  foreach my \(name (sort {\)studentnames{$a} <=>         \(studentnames{\)b}} keys %studentnames)  {     printf "%-8s %s\n", $name, \(studentnames{\)name}; } ```

  输出:

  ```perl Martha 14 Marty 16.5 Uri 19.6 Jason 25.2 Vivek 27 Socrates 29.5 Earl 31 Plato 45 Nitin 45

  ```

  例 2: 为了求解上述代码，具有相同值的键可以根据 ASCII 表排序如下:

  ```perl

  Perl program to demonstrate the

  Sorting of keys of the hash

  according to the values

  use strict; use warnings; use 5.010;

  Creating a hash of studentnames

  and their average score

  my %studentnames = ( Martha => 14, Vivek => 27, Earl => 31, Marty => 16.5, Jason => 25.2, Socrates => 29.5, Uri => 19.6, Nitin => 45, Plato => 45, );

  keys that have the same value

  will be sorted according the

  ASCII table

  foreach my $name (sort { \(studentnames{\)a} <=> \(studentnames{\)b} or                                 $a cmp $b } keys %studentnames) {     printf "%-8s %s\n", $name, \(studentnames{\)name}; } ```

  输出:

  ```perl Martha 14 Marty 16.5 Uri 19.6 Jason 25.2 Vivek 27 Socrates 29.5 Earl 31 Nitin 45 Plato 45

  ```

  说明:这里可以看到重点尼廷和柏拉图是按照 ASCII 表排序的。不管您运行代码多少次，输出都将保持不变。

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