Iteration of an algorithm - perl

Question

I wrote a program that load the data from a 2 columns file, made an algorithm calculation and then write the pair of elements in the file that have this coefficient and put them into an array called #blackPair. I would like to iterate N times the algorithm taking the datas from the file but not those that are in the #blackPair array.
I thought of something like this:
#!/usr/bin/perl
use strict;
use warnings;
use feature 'say';
my $iter;
my $startNode;
my $endNode;
my %k;
my %end;
my %node;
my %edge;
my #blackPair=();
my $counts=0;
my $inputfile = "file3";
################# DATA ABSORTION
open(DAT,$inputfile) || die("Could not open file!");
while(<DAT>)
{
my ($entry) = $_;
chomp($entry);
my ($startNode, $endNode) = split(/ /,$entry);
$k{$endNode}++;
$k{$startNode}++;
$edge{$startNode}{$endNode}=1;
$edge{$endNode}{$startNode}=1;
}
################# ALGORITHM
my $minCentrality=2;
foreach my $i (keys %edge) {
foreach my $j (keys %{$edge{$i}}){
my #couple =($j,$i);
if($i<$j){
if (($k{$i}-1) !=0 && ($k{$j}-1) !=0){
my $triangleCount=0;
#couple=($i,$j) if ($k{$i}<$k{$j});
foreach (keys %{$edge{$couple[0]}}){
$triangleCount++ if exists $edge{$couple[1]}{$_};
}
my $centrality=($triangleCount+1)/($k{$couple[0]}-1);
if ($centrality<$minCentrality){
$minCentrality=$centrality;
#blackPair=#couple;
}
}
}
}
}
foreach (#blackPair){
say;
}
Close(DAT);
The file is the following:
1 2
1 3
1 4
1 5
1 6
1 9
2 3
4 5
5 9
6 7
6 8
6 16
7 8
9 10
9 11
10 11
10 12
10 14
11 12
11 13
12 13
12 14
14 15
16 17
16 18
17 18
17 19
18 19
18 20
19 20
The first pair that appear in the #blackPair are the 6 and 1. After found them I would like that the program restart the search but avoiding to charge into the array the pairs 1 and 6. Doing that the second pair would be 6 and 16. I would like to repeat this process N times (for example N = 4). I thought to put before the while(<DAT>) in the "DATA ABSORTION" another while(counts<=4){ and inside the while(<DAT>) an if(<DATA> != #blackPair){. There is what I thought
while(counts <= 4) {
while(<DAT>)
{
if(<DAT> != #blackPair){
my ($entry) = $_;
chomp($entry);
.....
}
#### ALGORITHM
counts++;
}
But it doesn't work. Any help?
After 4 iteration, in the #blackPair there should be the following pairs:
6 1
16 6
9 1
9 5

Answer 1

<DAT> != #blackPair is definitely not what you want.
!= is for numerical comparison. You want to do either string comparison (the ne operator) or maybe use the smart match operator to check for list membership (~~ \#blackPair)
but using the right operator won't really help you, because #blackPair already has mangled the input data (#blackPair might contain the elements (6,1), corresponding to an original input line of "1 6\n")
Instead, how about updating your graph in each iteration?
for my $count (1..4) {
my $minCentrality = 2;
...
say join " ", #blackPair;
# now update the graph
delete $edge{$blackPair[0]}{$blackPair[1]};
delete $edge{$blackPair[1]}{$blackPair[0]};
$k{$blackPair[0]}--;
$k{$blackPair[1]}--;
} # next iteration