// create it here and provide it as an import.
// 倒序遍历2*len-1次：模拟数组循环（核心！易错点1）
，这一点在旺商聊官方下载中也有详细论述
Michael returned to Silicon Valley where, following a brief run at social media analytics company Klout, he joined Uber in 2013 as chief business officer and a close lieutenant to CEO Travis Kalanick. Over the next four years, he helped orchestrate one of the most aggressive expansions in corporate history, in which Uber raised nearly $15 billion and saw its valuation soar to roughly $70 billion.，更多细节参见Line官方版本下载
输入：["StockSpanner","next","next","next","next","next","next","next"], [[],[100],[80],[60],[70],[60],[75],[85]]，更多细节参见WPS下载最新地址