Keep unique node with lowest value on second index - php

Question

I am working on a multi dimensional array in PHP. How is it possible to select unique values from 0 index of a nested array which has lowest value on index 1?
Below is my sample data array
$data = array (
array(1, 9),
array(1, 3),
array(1, 5),
array(9, 2),
array(9, 7),
);
I am trying to get following array as a result
$result = array (
array(1, 3),
array(9, 2),
);

Answer 1

One way to do this could be to loop the array, use the indexes of the arrays and compare the second value. If the stored second value is greater than the new value, then overwrite it.
$data = array (
array(1, 9),
array(1, 3),
array(1, 5),
array(9, 2),
array(9, 7),
);
$result = [];
foreach ($data as $d) {
if (!isset($result[$d[0]])) {
$result[$d[0]] = $d;
continue;
}
if ($result[$d[0]][1] > $d[1]) {
$result[$d[0]] = $d;
}
}
print_r($result);
Demo

Answer 2

$data = array (
array(1, 9),
array(1, 3),
array(1, 5),
array(9, 2),
array(9, 7),
);
$result = [];
$lowest0 = null;
$lowest1 = null;
foreach($data as $row){
if($lowest0 === null || $row[0] < $lowest0[0] || ($row[0] === $lowest0[0] && $row[1] < $lowest0[1]))
{
$lowest0 = $row;
}
if($lowest1 === null || $row[1] < $lowest1[1] || ($row[1] === $lowest1[1] && $row[0] < $lowest0[0]))
{
$lowest1 = $row;
}
}
$result = [$lowest0,$lowest1];
var_dump($result);

Answer 3

Short and dirty:
$data = array (
array(1, 9),
array(1, 3),
array(1, 5),
array(9, 2),
array(9, 7),
);
foreach ($data as $row) {
($row[1] < ($uniq[$row[0]][1] ?? INF)) and $uniq[$row[0]] = $row;
}
var_dump($uniq);
Pass resulting array through array_values if re-indexing from 0 is important to you

Answer 4

This is as clear as mud, but it I made it as an example that it works without looping.
In short I use min and array_intersect(_key) to find where the minimum values are in the columns (with array_column).
//split out the two columns
$col0 = array_column($data, 0);
$col1 = array_column($data, 1);
// find minimum value in each
$min0 = min($col0);
$min1 = min($col1);
// find what keys this minimum value is in of each array
$mincol0 = array_intersect($col0, [$min0]);
$mincol1 = array_intersect($col1, [$min1]);
// use the previous and compare with minimum value of the other column
$result[] = $data[array_keys(array_intersect_key($col1, $mincol0),min(array_intersect_key($col1, $mincol0)))[0]];
$result[] = $data[array_keys(array_intersect_key($col0, $mincol1),min(array_intersect_key($col0, $mincol1)))[0]];
Var_dump($result);
https://3v4l.org/dgbDK
Since I apperantly missunderstood the question.
Here is another answer, still no need to loop the full array. That is just a waste of time.
Loop only unique column 0 values and find the minmum value in column 1 using array_intersect and array_intersect_key.
$col0 = array_column($data, 0);
foreach(array_unique($col0) as $item){
$intersect = array_intersect($col0, [$item]);
$res[] = min(array_intersect_key($data, $intersect));
}
var_dump($res);
https://3v4l.org/3UPQh