In Perl, how do I print hash keys in order of their (numerical) values?
hash, perl, sorting
Solution
Sort the keys by the values in the hash, then use the sorted keys to print.
for my $key ( sort { $ID_hash{$b} <=> $ID_hash{$a} } keys %ID_hash ) {
print join( "\t", $key, $ID_hash{$key} ), "\n";
}
This equivalent may be a little clearer:
my @sorted_keys = sort { $ID_hash{$b} <=> $ID_hash{$a} } keys %ID_hash ;
print "$_\t$ID_hash{$_}\n" for @sorted_keys;
Problem
I have a hash in which the keys are strings and the values are single-digit numbers; here's a slice of said hash: ``` 'f92a0d43-a230-4bfd-b580-9eac5e0ce6cf' => 7, '26c4b622-969f-4861-bbab-dd506ea4b00a' => 1, 'afb1f925-4109-4b1d-967f-3958106e0bc3' => 3, 'a099a6dc-0c66-4683-94c3-29d6ef6947fd' => 1, 'e71c4860-224d-4b8d-ae9e-4700e9e65a97' => 2, ``` I want print the keys in order of descending values. So for the slice listed there, the output would be: ``` 'f92a0d43-a230-4bfd-b580-9eac5e0ce6cf' => 7 'afb1f925-4109-4b1d-967f-3958106e0bc3' => 3 'e71c4860-224d-4b8d-ae9e-4700e9e65a97' => 2 '26c4b622-969f-4861-bbab-dd506ea4b00a' => 1 'a099a6dc-0c66-4683-94c3-29d6ef6947fd' => 1 ``` The order of keys with identical values does not matter. Answers to this question: In Perl, how can I print the key corresponding to the maximum value in a hash? suggest using the sort function; which I have: ``` my @values = sort { $b <=> $a } values %ID_hash; ``` What I am having trouble with is actually printing the keys in the order. I tried: ``` foreach(@values) { my $cur = $_; print "$ID_hash{$cur}\t$cur\n"; } ``` Which fails because I'm supplying values rather than keys. I know I can always just print the key/value pairs as a tab-separated file and use the Unix version of sort but I'm sure there's a way to do this with Perl. Any help will be much appreciated.