"I believe we've had a problem here," said Swigert. Lovell had to repeat the message to a stunned Mission Control: "Houston, we've had a problem."
方向遍历顺序说明下一个倒序（从右往左）先处理右侧，栈里存「右侧候选」上一个正序（从左往右）先处理左侧，栈里存「左侧候选」
。关于这个话题，safew官方下载提供了深入分析
ВСУ запустили «Фламинго» вглубь России. В Москве заявили, что это британские ракеты с украинскими шильдиками16:45
"There's no denying it was a challenging start," Dunstan said.