Question 40526 in PHP Question posted in
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The sum value of all nodes in the tree array in php

I have flat array like:

[
    {
        "id": "1",
        "parentId": "0",
        "cost": 1000
    },
    {
        "id": "2",
        "parentId": "1",
        "cost": 2000
    },
    {
        "id": "3",
        "parentId": "2",
        "cost": 4000
    },
    ...
]

Requirement:

  • convert flat array to tree array –> (DONE)
  • sum of each id is the total price of it and its child

now the problem appears:

  • should summation be done before or after converting from flat array to tree array

This is my code is try convert flat to tree:

public function buildTree(array $flat)
    {
        $grouped = [];
        $fnBuilder = function ($companies) use (&$fnBuilder, $grouped) {
            foreach ($companies as $k => $company) {
                $id = $company['id'];
                if (isset($grouped[$id])) {
                    $company['children'] = $fnBuilder($grouped[$id]);
                }
                $companies[$k] = $company;
            }
            return $companies;
        };
        return $fnBuilder($grouped[0]);
    }

My expect result is like:

[
    {
        "id": "1",
        "sum": 7000,
        "children": [
            {
                "id": "2",
                "sum": 6000,
                "children": [
                    {
                        "id": "3",
                        "sum": 4000,
                    },

I wonder if it’s possible to handle the summing inside the buildTree?

My idea is to have a tree and then handle the sum of sublevels, but i can’t handle assigning the sum to the parent element
Tags:

2

Answers


  1. 0

    I created a class and incorporated your ideas.

    class TreeBuilder {
    private $flatArr;
    private $idToNode;

    public function __construct($flatArr) {
        // Keep the flat arr in case we need it.
        $this->flatArr = $flatArr;
        // Create an array to lookup a node to determine if it exists.
        $this->idToNode = array_combine(array_column($flatArr, 'id'), $flatArr);
    }

    public function buildTree() {
        // create an empty array to hold root nodes
        $roots = [];
        // iterate through each node and add it to its parent's children list
        foreach ($this->flatArr as &$node) {
            $id = $node['id'];
            $parentId = $node['parentId'];
            if (isset($this->idToNode[$parentId])) {
                $this->out("add child to $parentId " . print_r($node, true));
                $parentNode = &$this->idToNode[$parentId];
                if ( isset($parentNode['children']) ) {
                    $parentNode['children'] = [&$this->idToNode[$id]];
                } else {
                    $parentNode['children'][] = &$this->idToNode[$id];
                }
                // $children[] = &$node;
            } else {
                $this->out("add to root " . print_r($node, true));
                $roots[] = &$this->idToNode[$id];
            }
        }
        // calculate the sum of each node and its children recursively
        foreach ($roots as &$root) {
            $this->calculateSum($root);
        }
        return $roots;
    }

    private function calculateSum(&$node) {
        // calculate the sum of the current node
        $node['sum'] = $node['cost'];
        // recursively calculate the sum of the children nodes
        $children = &$node['children'];
        if (isset($children)) {
            foreach ($children as &$child) {
                $node['sum'] += $this->calculateSum($child);
            }
        }
        return $node['sum'];
    }

    private function out($s) {
        echo "$sn";
    }
}
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  2. 0

    You could build the tree without recursion, and then use recursion to update the sum, in post-order depth first order:

    function buildTree(array $flat) {
    foreach ($flat as ["id" => $id, "cost" => $sum]) {
        $keyed[$id] = ["id" => $id, "sum" => $sum];
    }
    foreach ($flat as ["id" => $id, "parentId" => $parentId]) {
        if (isset($keyed[$parentId])) {
            $keyed[$parentId]["children"][] = &$keyed[$id]; 
        } else {
            $root = &$keyed[$id];
        }
    }
    function updateSum(&$node) {
        foreach ($node["children"] ?? [] as &$child) {
            $node["sum"] += updateSum($child);
        }
        return $node["sum"];
    }
    updateSum($root);
    return $root;
}

    Example run:

    $flat = json_decode('[
    {
        "id": "1",
        "parentId": "0",
        "cost": 1000
    },
    {
        "id": "2",
        "parentId": "1",
        "cost": 2000
    },
    {
        "id": "3",
        "parentId": "2",
        "cost": 4000
    }
]', true);

$root = buildTree($flat);
print_r($root);
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