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// 步骤3：从后往前遍历数组（反向遍历更易理解，每个元素只入栈/出栈一次），详情可参考服务器推荐
During the ”snowball Earth” period about 700m years ago, Earth’s climate shut down. The planet was encased in ice and insulated from seasonal variations: spring, summer, autumn and winter all stopped. Or at least that was the theory.，更多细节参见91视频
Andrew can also tuck his mouse and keybord out of the way