需要索引（如算距离、下标）：栈存索引，用 nums[stack.at(-1)] 取值比较。
Ultimately, the most rigorous traceability solutions, including QR codes and microchips, won't be useful if people don't actually check them as a condition of making their purchases. Imitators can simply counterfeit QR code labels, for example.
，详情可参考谷歌浏览器【最新下载地址】
Kushner, and other financers from the Saudi and Qatari sovereign wealth funds backing the Paramount bid, had agreed not to take any controlling roles - such as seats on the board - in exchange for their investments.
No evidence has been presented that these safeguards are insufficient to continue to protect Android users as they have for the entire seventeen years of Android’s existence. If Google’s concern is genuinely about security rather than control, it should invest in improving these existing mechanisms rather than creating new bottlenecks and centralizing control.
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