Re: sorting a hash / 2008-06-01

dn.perl@xxxxxxxxx wrote:
I want to sort a hash. The hash contains a list of cities and their
temperature and I want the 4 cities with max temp. The problem is that
the city-names are one extra level deep with the state-name coming in-
between. I wondered whether I should build the hash differently. A
different format would be: state_city, with the underbar separating
the state and the city.
$hash{Calif_Cupertino}{max_temp} = 38 ;
instead of
$hash{Calif}{Cupertino}{max_temp} = 38 ;


my %hash = () ;
$hash{Calif}{San Jose}{max_temp} = 84 ;
$hash{Calif}{San Fran}{max_temp} = 94 ;
$hash{Calif}{Cupertino}{max_temp} = 38 ;
$hash{Calif}{Fremont}{max_temp} = 66 ;
$hash{Texas}{Dallas}{max_temp} = 72 ;
$hash{Texas}{Austin}{max_temp} = 96 ;
$hash{Texas}{Fort Worth}{max_temp} = 62 ;
$hash{Mass}{Boston}{max_temp} = 96 ;
$hash{Mass}{Framingham}{max_temp} = 55 ;
$hash{Mass}{Worcester}{max_temp} = 55 ;

How do I sort this hash, please?

$ perl -le'
my %hash = (
Calif => {
"San Jose" => { max_temp => 84 },
"San Fran" => { max_temp => 94 },
Cupertino => { max_temp => 38 },
Fremont => { max_temp => 66 },
},
Texas => {
Dallas => { max_temp => 72 },
Austin => { max_temp => 96 },
"Fort Worth" => { max_temp => 62 },
},
Mass => {
Boston => { max_temp => 96 },
Framingham => { max_temp => 55 },
Worcester => { max_temp => 55 },
},
);

print "City: $_->[0] Temperature: $_->[1]"
for (
sort { $b->[ 1 ] <=> $a->[ 1 ] }
map { my $hash = $_; map [ $_, $hash->{ $_ }{ max_temp } ], keys %$hash }
values %hash
)[ 0 .. 3 ];
'
City: Austin Temperature: 96
City: Boston Temperature: 96
City: San Fran Temperature: 94
City: San Jose Temperature: 84




John
--
Perl isn't a toolbox, but a small machine shop where you
can special-order certain sorts of tools at low cost and
in short order. -- Larry Wall
.

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