Sorting in
Perl can be done with the use of a pre-defined function 'sort'. This function uses a quicksort algorithm to sort the array passed to it.
Syntax: sort @array
Returns: a sorted array
Sorting of an array that contains strings in the mixed form i.e. alphanumeric strings can be done in various ways with the use of sort() function.
Example:
Input : Key_8, pub_12, pri_4 (array of strings)
Output : pri_4 Key_8 pub_12
Sorting of such arrays is done by extracting the numbers from the strings which can be done in two ways:
- Using substr() Function: For the purpose of comparing the strings using the numbers, it is very essential to get numbers from strings. Based on the numbers we are going to sort the array of strings. substr() function is used to extract these numbers from the string. This function takes, no. of characters in the string excluding the numeric, as the parameter.
Note: All the alphanumeric strings in the array must be of the same size.
Example:
Output:
prin_4 Keys_8 pubg_12
-
Using Regular Expressions : Executing above code is a tough job if the alphanumeric string is a little bit complex, hence, for more simplicity, we can use Regular Expressions.
For Example- if the array consists "Keys_8_keys" then it's difficult to handle such case, hence for proper filtering of the number from the string, Regular Expressions are used.
Note: This method doesn't care if the alphanumeric strings are of different sizes.
usestrict;
use5.010;
# Sample string to extract
# number from
my$str='Key_8_key';
# Regular expression to extract the number
my($number)=$str=~ /(\d+)/;
# Printing the extracted number
print"Number Extracted from Key_8_key is $number\n";
# Defining the array with
# Alphanumeric strings
my@x=qw(pri_4 Key_8_key pubg_12);
# Array before sorting
print"\nArray Before sorting\n";
printjoin" ",sort@x;
# Calling the sort function
# with Regular Expression
my@y=sort{($a=~ /(\d+)/)[0]<=>($b=~ /(\d+)/)[0]}@x;
# Printing the Array after sorting
print"\n\nArray After sorting\n";
printjoin" ",@y;
Output:
Number Extracted from Key_8_key is 8
Array Before sorting
Key_8_key pri_4 pubg_12
Array After sorting
pri_4 Key_8_key pubg_12
String without a Number: If the array consists of strings in which some of the strings don't have a number in it, then 0 can be used in place of that number. To check if there is no number in the string, following code is used:
my @y = sort { (($a =~ /(\d+)/)[0] || 0) (($b =~ /(\d+)/)[0] || 0) } @x;
Output:
Key pri_4 pubg_12
Sorting using a Subroutine: For better modularization of code we can create separate function or subroutine in Perl and perform the sorting operation with the use of that subroutine. sort() function here takes the subroutine name as the parameter and calls the subroutine which holds the definition for sorting.
Output:
pri_4 Key_8 pubg_12
