原文： https://github.com/elarity/data-structure-php-clanguage/blob/master/8.%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B9%8B%E6%A0%91%E7%9A%84%E5%9F%BA%E6%9C%AC%E6%9E%AF%E7%87%A5%E6%A6%82%E5%BF%B5%EF%BC%88%E4%B8%80%EF%BC%89.md