Union of Two Hashes

[Rajiv]

I want to find the union of two hashes. I tried the option of merging the two hashes, but found that relatively slower. Can anybody suggest me a good optimized code for getting the union of two hashes. The option that i am trying looks like this:

foreach $k (sort keys %hash1) {
  if (exists($hash2{$k})) {
     $matchWords++;
   } 
}

This snippet runs faster than merging. I don't understand how ??

Originally posted as a Categorized Question.

[maverick]

The question is a bit confusing...you ask for a union, but you code snippet looks like you're looking for the intersection. Union first. For small hashes this is really quick:

%union = (%first, %second);

For large:

while (($k,$v) = each %first) { $union{$k} = $v; }
while (($k,$v) = each %second) { $union{$k} = $v; }

(makes sense once you consider the memory usage for the first snippet.

For intersection, all you really need to do is change $matchWords to $matchWords{$k}++ the iterate of then matchWords looking for values == 2