合并具有相同值的数组

Question

I have array like this

$arr=[["a","b"],["b","c"],["d","e"],["f","c"]];

if sub arrays share same value they should be be merged to one array

expected output:

$arr=[["a","b","c","f"],["d","e"]];

I`m trying to avoid doing foreach inside foreach for solving this.

Answer 1

It seems your inner arrays always have 2 items. so nested loops aren't necessary. Here is a solution which I originally wrote in JS but it should work just as good and most efficient in PHP:

$arr=[["a","b"],["b","c"],["d","e"],["f","c"],["h","e"]];
$output = [];
$outputKeys = [];
$counter = 0;
foreach($arr as $V) {
    if(!isset($outputKeys[$V[0]]) && !isset($outputKeys[$V[1]])) {
        $output[$counter] = [$V[0], $V[1]];
        $outputKeys[$V[0]] = &$output[$counter];
        $outputKeys[$V[1]] = &$output[$counter];
        $counter++;
    }
    elseif(isset($outputKeys[$V[0]]) && !isset($outputKeys[$V[1]])) {
        array_push($outputKeys[$V[0]], $V[1]);
        $outputKeys[$V[1]] = &$outputKeys[$V[0]];
    }
    elseif(!isset($outputKeys[$V[0]]) && isset($outputKeys[$V[1]])) {
        array_push($outputKeys[$V[1]], $V[0]);
        $outputKeys[$V[0]] = &$outputKeys[$V[1]];
    }
}
var_dump($output); // [["a","b","c","f"],["d","e","h"]]

DEMO (click the execute button)

Pointers are your friends. Use them :)

Answer 2

This is solution I get for now.

    $arr=[["a","b","c","f"],["d","e"]];
    $sortedArray = sortFunction($arr,0,array());

function sortFunction($old,$index,$new) {
    if ($index == sizeof($old)) return $new;

    for ($i = 0; $i<sizeof($new); $i++) {
        if (count(array_intersect($new[$i],$old[$index]))) {
            $new[$i] = array_unique(array_merge($old[$index],$new[$i]), SORT_REGULAR);
            return sortFunction($old,$index + 1,$new);
        }
    }

    $new[] = $old[$index];
    return sortFunction($old,$index + 1,$new);
}

Answer 3

The following algorithm should do what you want. It simply checks through each item and checks if it already exists in the newly created array, and if it does it adds it to that item instead of a new one:

<?php

$arr=[["a","b"],["b","c"],["d","e"],["f","c"]];

$newArr = [];

foreach ($arr as $items) {
    $newKey = null;

    foreach ($items as $item) {
        foreach ($newArr as $newItemsKey => $newItems) {
            if (in_array($item, $newItems)) {
                $newKey = $newItemsKey;

                break 2;
            }
        }
    }

    if ($newKey !== null) {
        $newArr[$newKey] = array_merge($newArr[$newKey], $items);
    } else {
        $newArr[] = $items;
    }
}

$newArr = array_map('array_unique', $newArr);

print_r($newArr);

Output :

Array
(
    [0] => Array
        (
            [0] => a
            [1] => b
            [3] => c
            [4] => f
        )

    [1] => Array
        (
            [0] => d
            [1] => e
        )

)

DEMO