需要元素值：栈存值，或答案存索引后用 nums[res[i]] 取值。
(~70 host syscalls from Sentry)。关于这个话题，新收录的资料提供了深入分析
Complete coverage。新收录的资料对此有专业解读
This change prevents projects from unintentionally pulling in hundreds or even thousands of unneeded declaration files at build time.