CODEWITHSUNDEEP
perlsortinghash
Musicode
Musicode

Reputation: 661

Basic Perl hash sorting by key, by value, but also by key AND value

Okay, I have a Perl program I'm writing which has a hash of values that I have collected (in a whole separate program altogether) and have fed to this Perl script. This hash is a hash of (string,string).

I want to sort the values 3 ways: First, I want to sort by key. I figured this is easy, you do it exactly the way you would think, using Perl's built in sort function, looping over the keys, and printing/storing/whatevering with each one as they are sorted. 

foreach my $name (sort keys %planets) {
    printf "%-8s %s\n", $name, $planets{$name};
}

Second, I want to sort by value. Again, this is easy, use the sort function and loop over:

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

Third, My question is, how do I sort by value, but for any ties in values between two keys, I sort out first the value which has the greater Asciibetical key. Example:

Red => 50
Yellow => 75
Blue => 75

is sorted to this, since 'Yellow' is greater asciibetically than 'Blue' 
Red 50
Blue 75
Yellow 75

Upvotes: 3

Views: 154

Answers (1)

ysth
ysth

Reputation: 98388

On a tie, the comparison operators will return 0, so you can chain several comparisons with ||:

 sort { $planets{$a} <=> $planets{$b} || $a cmp $b }

Upvotes: 10

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