Sets Difference algorithm

Lets assume you have two sets as follows:

example sets:

Set A

1
2
3
4

Set B

3
4
5
6

now we want to get difference of these sets:

(assume a cleared (0) flag "added" for each element of set B)

algorithm:

1. for each element E in set B, iterate over elements in set A
    i. if value of element E is found in set A, remove that entry from A
   ii. if value of element E is not found in set A, set (1) "added" flag of element E
4. Remaining elements in set A, represents set difference A-B
5. elements in set B, having flag "added" set (1), represents set difference B-A
6. elements in set B, having flag "added" cleared(0), represents set intersections
7. All remaining elements in set A and value of all elements in set B represents union of set A and B

result:

Set A

1
2

Set B

3
4
5 -> added
6 -> added

A-B = 1,2
B-A = 5,6

A intersection B = 3,4
A union B = 1,2,3,4,5,6

optimizations:

if set A is sorted, iterated over elements of set A, until element value in set A is less than element E of set B
similarly, further optimizations are possible when both sets are sorted.

perl cpan install module

> perl -MCPAN -e shell
> install module_name

e.g.:
> install Net::DNS::Check

update perl modules to latest versions

Ubuntu environment:

Execute:

> sudo apt-get install cpanminus

> sudo cpanm App::cpanoutdated

> sudo cpan-outdated -p | cpanm

Update single module from CPAN: download, build and install

cpanm Net::DNS
cpanm LWP