如何入门科学上网

每当我们希望通过 Facebook 与国际友人聊天,想在 Twitter 看川普吹嘘,或是想上 Youtube 看一段精彩的视频,又或是想上 Wikipedia 了解一个新事物……在国内正常的访问这些境外网站,通常只能会在漫长的等待后得到一个“404 Not Found”抑或是其他错误提示。这时候,我们的上网受到了 GFW 阻碍,为越过这道障碍,我们就需要科学上网。

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2018 BUPT Summer Training #1 (恢复训练) 部分题解(仍会更新)

原题链接

A. Treasure Island

Time limit: 2000 ms
Memory limit: 262144 kB

Pirate John Silver has found a map depicting exactly one island in a sea. The map is a piece of cloth divided into cells: n cells in height and m cells in width. John Silver knows that every cell denotes either land or water, but some of the cells are erased, and now it’s absolutely impossible to say what these cells represent.
Help John Silver to restore the map of the island. An island is a non-empty set of land cells connected in four directions (up, down, left and right).
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