Nagoya.php vol.9 プログラミング問題解答例

1.初級編.php

<?php
$data = [
    [
        'id' => 1,
        'parent_id' => 0,
        'value' => '親1',
    ],
    [
        'id' => 2,
        'parent_id' => 0,
        'value' => '親2',
    ],
    [
        'id' => 3,
        'parent_id' => 1,
        'value' => '子1-1',
    ],
    [
        'id' => 4,
        'parent_id' => 1,
        'value' => '子1-2',
    ],
    [
        'id' => 5,
        'parent_id' => 2,
        'value' => '子2-1',
    ],
];

function render()
{
    global $data;

    // 親だけを抽出.
    $parents = array_filter($data, function ($node) {
        return $node['parent_id'] === 0;
    });

    echo '<ul>';

    // 親のループ.
    foreach ($parents as $parent) {

        echo "<li>{$parent['value']}";

        // 自分の子だけを抽出.
        $children = array_filter($data, function ($node) use ($parent) {
            return $node['parent_id'] === $parent['id'];
        });

        // 子のループ.
        if ($children) {
            echo '<ul>';
            foreach ($children as $child) {
                echo "<li>{$child['value']}</li>";
            }
            echo '</ul>';
        }

        echo '</li>';
    }

    echo '</ul>';
}

render();

2.テストデータ.php

<?php
return [
    [
        'id' => 1,
        'parent_id' => 0,
        'value' => '親1',
    ],
    [
        'id' => 2,
        'parent_id' => 0,
        'value' => '親2',
    ],
    [
        'id' => 3,
        'parent_id' => 1,
        'value' => '子1-1',
    ],
    [
        'id' => 4,
        'parent_id' => 1,
        'value' => '子1-2',
    ],
    [
        'id' => 5,
        'parent_id' => 2,
        'value' => '子2-1',
    ],
    [
        'id' => 6,
        'parent_id' => 4,
        'value' => '孫1-2-1',
    ],
    [
        'id' => 7,
        'parent_id' => 3,
        'value' => '孫1-1-1',
    ],
    [
        'id' => 8,
        'parent_id' => 7,
        'value' => 'ひ孫1-1-1-1',
    ],
    [
        'id' => 9,
        'parent_id' => 5,
        'value' => '孫2-1-1',
    ],
    [
        'id' => 10,
        'parent_id' => 5,
        'value' => '孫2-1-2',
    ],
    [
        'id' => 11,
        'parent_id' => 2,
        'value' => '子2-2',
    ],
    [
        'id' => 12,
        'parent_id' => 4,
        'value' => '孫1-2-2',
    ],
    [
        'id' => 13,
        'parent_id' => 9,
        'value' => 'ひ孫2-1-1-1',
    ],
    [
        'id' => 14,
        'parent_id' => 5,
        'value' => '孫2-1-3',
    ],
    [
        'id' => 15,
        'parent_id' => 2,
        'value' => '子2-3',
    ],
];

2.再帰化.php

<?php
$data = require __DIR__ . '/data.php';

function renderSubtree($parentId)
{
    global $data;

    // 指定された親だけを抽出.
    $parents = array_filter($data, function ($node) use ($parentId) {
        return $node['parent_id'] === $parentId;
    });

    // 見つからなければ何もしない.
    if (!$parents) {
        return;
    }

    echo '<ul>';

    // 親のループ.
    foreach ($parents as $parent) {

        echo "<li>{$parent['value']}";

        // 子以下を出力.
        renderSubtree($parent['id']);

        echo '</li>';
    }

    echo '</ul>';
}

renderSubtree(0);

3.CLI対応.php

<?php
$data = require __DIR__ . '/data.php';

class Renderer
{
    const CLI_INDENT = '  ';

    private $data;
    private $indents;
    private $isCli;

    public function __construct(array $data)
    {
        $this->data = $data;
        $this->indents = -1;
        $this->isCli = php_sapi_name() === 'cli';
    }

    public function renderSubtree($parentId)
    {
        // 指定された親だけを抽出.
        $parents = array_filter($this->data, function ($node) use ($parentId) {
            return $node['parent_id'] === $parentId;
        });

        // 見つからなければ何もしない.
        if (!$parents) {
            return;
        }

        $this->openTree();

        // 親のループ.
        foreach ($parents as $parent) {

            $this->openNode($parent['value']);

            // 子以下を出力.
            $this->renderSubtree($parent['id']);

            $this->closeNode();
        }

        $this->closeTree();
    }

    private function openTree()
    {
        if ($this->isCli) {
            $this->indents++;
        } else {
            echo '<ul>';
        }
    }

    private function closeTree()
    {
        if ($this->isCli) {
            $this->indents--;
        } else {
            echo '</ul>';
        }
    }

    private function openNode($value)
    {
        if ($this->isCli) {
            echo str_repeat(self::CLI_INDENT, $this->indents);
            echo "* {$value}\n";
        } else {
            echo "<li>{$value}";
        }
    }

    private function closeNode()
    {
        if (!$this->isCli) {
            echo '</li>';
        }
    }
}

$renderer = new Renderer($data);
$renderer->renderSubtree(0);