Helvetic Coding Contest 2019 A2 题意:给一个长度为 n 的01序列 y.认为 k 合法当且仅当存在一个长度为 n 的01序列 x,使得 x 异或 x 循环右移 k 位的 01 串得到 y .问合法的 k 的个数. \(n \le 2*10^5\) key:找规律 考虑如何check一个 k 是否合法.那么对于所有的 i 和 i-k 在模 n 的意义下,如果 y 的第 i 位为 0 则二者必须不同,否则必须相同.这样可以用并查集判断是否合法.实际上是把相同的缩起来后…
Description Tonight is brain dinner night and all zombies will gather together to scarf down some delicious brains. The artful Heidi plans to crash the party, incognito, disguised as one of them. Her objective is to get away with at least one brain,…
Description Heidi has finally found the mythical Tree of Life – a legendary combinatorial structure which is said to contain a prophecy crucially needed to defeat the undead armies. On the surface, the Tree of Life is just a regular undirected tree w…
Description The zombies are gathering in their secret lair! Heidi will strike hard to destroy them once and for all. But there is a little problem... Before she can strike, she needs to know where the lair is. And the intel she has is not very good.…
Description Further research on zombie thought processes yielded interesting results. As we know from the previous problem, the nervous system of a zombie consists of n brains and m brain connectors joining some pairs of brains together. It was obser…
