Question

my data is in a file basically like :

a
2
b
6
a
4
f
2
b
1
a
7

I have this hash :

%hash = {
    a => 2,
    b => 6,
    a => 4,
    f => 2,
    b => 1, 
    a => 7,
};

How can I find duplicate keys and among them? I want the one that have the biggest value.

Desired output:

a-->7 
b-->6
f-->2

Answer 1

If you only ever want the highest value for a particular key, then add the logic into your assignment to the hash. At the point you would add a key and a value, do something like this:

unless (exists $hash{$key} and $hash{$key} >= $value)
{
   $hash{$key} = $value;
}

If you need to preserve all values, then make each key point to an array of values. Here is what your assignment would look like:

#Add an element to the array of values for this key.
push @{ $hash{$key} }, $value;

Here is a nice way to find the maximum value in the resultant array for a given key:

use List::Util qw/max/;

print max @{ $hash{$key} };