层次树遍历(Laravel/PHP)

class Category extends Model
{
    public function children()
    {
        return $this->hasMany(Category::class, 'parent_id');
    }

    public function parent()
    {
        return $this->belongsTo(Category::class, 'parent_id');
    }
}

function dfs($category)
{
    echo $category->name . "\n";
    foreach ($category->children as $child) {
        dfs($child);
    }
}

$rootCategory = Category::find(1); // 假设根分类ID为1
dfs($rootCategory);

function bfs($rootCategory)
{
    $queue = [$rootCategory];
    while (!empty($queue)) {
        $category = array_shift($queue);
        echo $category->name . "\n";
        foreach ($category->children as $child) {
            $queue[] = $child;
        }
    }
}

$rootCategory = Category::find(1); // 假设根分类ID为1
bfs($rootCategory);

function dfsSafe($category, $visited = [])
{
    if (in_array($category->id, $visited)) {
        return;
    }
    $visited[] = $category->id;
    echo $category->name . "\n";
    foreach ($category->children as $child) {
        dfsSafe($child, $visited);
    }
}

$rootCategory = Category::find(1);
dfsSafe($rootCategory);