How to conditionally merge a multi-dimensional array - php

Question

I have a multi-dimensional array:
Array
(
[10] => Array
(
[from] => Jack
[to] => Terry
[Bribe] => 0
[Joke_Payment] => 0
[Corrupt_Support] => 1
[Legitimate_Support] => 0
[Obfuscation] => 1
[Legal_Enforcement] => 0
[Whistleblower] => 0
)
[11] => Array
(
[from] => Terry
[to] => Jack
[Bribe] => 0
[Joke_Payment] => 0
[Corrupt_Support] => 1
[Legitimate_Support] => 0
[Obfuscation] => 0
[Legal_Enforcement] => 1
[Whistleblower] => 0
)
)
I want to update the above array to like this: have a 1 (going from from to to) and a -1 for the opposite direction, a 2 signify for "both directions.
Array ( [10] => Array
(
[from] => Jack
[to] => Terry
[Bribe] => 0
[Joke_Payment] => 0
[Corrupt_Support] => 2
[Legitimate_Support] => 0
[Obfuscation] => 1
[Legal_Enforcement] => -1
[Whistleblower] => 0
) }
How can I firstly calculate their intersect and then update the original array?
They will have the same amount to keys, and when from matches to, and to matches from element, I want to combine these two arrays into one. A '1' is used to indicate that the property relates in the from to to direction, and a -1 indicates that the property goes in the reverse direction (from to to from).
My current code is:
$fileRelation = explode("\r", $end);
$rowsRelation = array_map('str_getcsv', $fileRelation);
$headerRelation = array_shift($rowsRelation);
$csvArrRelation = array();
$countR = count($headerRelation);
foreach ($rowsRelation as $key => &$row) {
$index = 2;$sum = 0;$sumArr = array();
while ($index < $countR) {
if ($row[$index]>0) {
$sumArr[$sum]=$index; //store row $headerRelation index
$sum++;
}
$index++;
}
if($sum > 0){ //remove element if no relationship exist
foreach ($csvArrRelation as $k => $a) {
if (in_array($row[0], $csvArrRelation[$k]) && in_array($row[1], $csvArrRelation[$k])){
$p = array_values($a);$i = 2;$cp= count($p);
while($i < $cp ){
if($row[$i] == $p[$i]){
$a[$headerRelation[$i]] += $row[$i];
}else{
$a[$headerRelation[$i]] -= $row[$i];
}
$i++;
}
unset( $rowsRelation[$key] );
}
}
$csvArrRelation[] = array_combine($headerRelation, $row);
}
}

Answer 1

I won't write this for you, but here is a good start:
$newRelations = [];
$deletions = [];
foreach ($rowsRelation as $key1 => $row1)
{
foreach ($rowsRelation as $key2 => $row2)
{
// Don't compare with self
if ($key1 != $key2)
{
// Have we found a reverse match?
if (
$row1['from'] == $row2['to'] &&
$row1['to'] == $row2['from']
)
{
$newRelations[] = myMerge($row1, $row2);
$deletions[] = $key1;
$deletions[] = $key2;
}
}
}
}
// Delete old rows
foreach ($deletions as $deleteKey)
{
unset($rowsRelation[$deleteKey]);
}
// Add in new rows
$rowsRelation = array_merge($rowsRelation, $newRelations);
function myMerge(array $row1, array $row2)
{
// todo
}
My strategy is to compare each row with every other, and if a reverse match is found, we know a merge is due. To avoid corrupting the foreach loops, I add the new array value to a different array, and log which keys I wish to delete from the original. These are then merged/deleted after the work is done.

Answer 2

I assume this is some kind of game, so let's call "player 1" the player whose name appears in "from" field and "player 2" the one whose name appears in "to" field.
According to what I understood, you consider player 1's values positive and player 2's negative. Then you sum both values in "from player 1 to player 2" record and discard "from player 2 to player 1" record.
According to that rule, Corrupt_Support should end up with a value of 0, not 2.
Basically, after merging your records, you will not be able to tell the difference between no actions at all and actions that have cancelled each other.
Besides, there is no rule to chose a "winner", i.e. which "from" player will be retained, leading to potentially impractical results.
If you have 3 players Abe, Bob and Cal, you can end up with any possible order, for instance
["Abe vs Bob", "Bob vs Cal" and "Cal vs Abe"] or
["Abe vs Bob", "Abe vs Cal" and "Cal vs Bob"].
Looking up actions for Bob will be rather problematic in the latter case.
Now if you still want to do that, here is a way that takes advantage of PHP hash tables to speed up the merge and choses the "winner" according to alphabetic order:
// use "from player 1 to player 2" relation as key
foreach ($relations as $r) $relation_pairs[$r['from'].'+'.$r['to']] = $r;
// pick the "winners" according to alphabetic order
ksort ($relation_pairs);
// merge relations
while (list($k,$r) = each($relation_pairs)) // this will take elements deletion into account immediately, contrary to foreach
{
$symetric = $r['to'].'+'.$r['from'];
if (isset($relation_pairs[$symetric])) // found a symetric relation
{
foreach ($relation_pairs[$symetric] as $field=>$value) // combine all numeric fields
if (is_numeric ($value))
$relation_pairs[$k][$field] -= $value;
unset ($relation_pairs[$symetric]); // get rid of symetric relation
}
}
$compressed_relations = array_values ($relation_pairs); // get rid of keys