Get parent and leaf ids from tree builder - php

Question

I'm building a tree feature for my app. My tree has infinite level. I'm using this functions to build my tree (you can try my code here https://onlinephp.io/c/a50bc):
function build(array $array): array
{
if (count($array) <= 0) {
return [
'leaf_ids' => [],
'parent_ids' => [],
'tree' => [],
];
}
$groupByParent = [];
foreach ($array as $arr) {
$parent_id = empty($arr['parent_id']) ? 0 : $arr['parent_id'];
$groupByParent[$parent_id][] = $arr;
}
return makeTree($groupByParent, $groupByParent[0]);
}
function makeTree(array &$parentList, array $items): array
{
$tree = [];
$leafIds = [];
$parentIds = [];
foreach ($items as $item) {
if (isset($parentList[$item['id']])) {
$item['children'] = makeTree($parentList, $parentList[$item['id']])['tree'];
}
if (!isset($item['children'])) {
$leafIds[] = $item['id'];
} else {
$parentIds[] = $item['id'];
}
$tree[] = $item;
}
return ['tree' => $tree, 'leaf_ids' => $leafIds, 'parent_ids' => $parentIds];
}
$array = [
[
'id' => 1,
'parent_id' => NULL,
'value' => 'Hi',
],
[
'id' => 2,
'parent_id' => NULL,
'value' => 'Bye',
],
[
'id' => 3,
'parent_id' => 1,
'value' => 'Hey',
],
[
'id' => 4,
'parent_id' => 1,
'value' => 'Hello',
],
[
'id' => 5,
'parent_id' => 2,
'value' => 'Cya',
],
[
'id' => 6,
'parent_id' => 5,
'value' => 'Byebye',
],
];
print_r(json_encode(build($array), JSON_PRETTY_PRINT));
I'd like to get the list of leafs and parents but my code doesn't work at all. At the end I don't have all parents ids and my leaf_ids array is empty.
I got this output:
{
"tree": [
{
"id": 1,
"parent_id": null,
"value": "Hi",
"children": [
{
"id": 3,
"parent_id": 1,
"value": "Hey"
},
{
"id": 4,
"parent_id": 1,
"value": "Hello"
}
]
},
{
"id": 2,
"parent_id": null,
"value": "Bye",
"children": [
{
"id": 5,
"parent_id": 2,
"value": "Cya",
"children": [
{
"id": 6,
"parent_id": 5,
"value": "Byebye"
}
]
}
]
}
],
"leaf_ids": [],
"parent_ids": [
1,
2
]
}
The output that I want for leaf_ids is: "leaf_ids": [3,4,6] and for parent_ids: "parent_ids": [1,2,5].
How can I do to return leafs and parents list ?

Answer 1

When you make the recursive call, you will need to merge the results for leaf_ids and parent_ids obtained from sub tree results as well, like below:
<?php
if (isset($parentList[$item['id']])) {
$sub_tree = makeTree($parentList, $parentList[$item['id']]);
$item['children'] = $sub_tree['tree'];
$leafIds = array_merge($leafIds, $sub_tree['leaf_ids']);
$parentIds = array_merge($parentIds, $sub_tree['parent_ids']);
}
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