思路：倒序遍历 2 倍长度 + 取模模拟循环 + 单调栈。用 i % len 映射到真实索引，仅当 i < len 时记录答案。
贫困是顽疾，“顽”在成因复杂、难以根除、极易反复。
，推荐阅读快连下载安装获取更多信息
（本报记者赵成、吴丹、朱隽、王昊男、侯琳良、杨文明、王云娜、刘军国、李心萍、寇江泽、李林蔚、常钦、刘新吾、郑洋洋、李俊杰）。业内人士推荐heLLoword翻译官方下载作为进阶阅读
By WWII, scientists had already begun looking at alternative gelling substances for routine use in bacteriology, but concluded that agar was still better as it is both firmer and easier to handle. Today, some specialized microbiology applications use the colloid carrageenan (extracted from red seaweed Chondrus crispus, or “Irish Moss”), a more transparent and less auto-fluorescent alternative to agar (agar emits its own background fluorescence when excited by light). However, for routine bacteriological use, carrageenan is more difficult to dissolve, requires higher concentrations, can degrade at high temperatures, and forms weaker gels, which may result in puncturing its surface during the plating of cells.