CodeForces721B R - Passwords

最新推荐文章于 2022-06-29 14:36:36 发布

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最新推荐文章于 2022-06-29 14:36:36 发布 · 1.5k 阅读

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题目要求计算在最佳和最糟情况下，Vanya找到正确密码所需的时间。Vanya按密码长度递增顺序尝试，且在连续输错K次后会被锁定5秒。最佳情况是第一试就成功，最糟情况是每次尝试都失败直到最后。需要考虑冷冻期的影响。

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Vanya is managed to enter his favourite site Codehorses. Vanya uses n distinct passwords for sites at all, however he can’t remember which one exactly he specified during Codehorses registration.

Vanya will enter passwords in order of non-decreasing their lengths, and he will enter passwords of same length in arbitrary order. Just when Vanya will have entered the correct password, he is immediately authorized on the site. Vanya will not enter any password twice.

Entering any passwords takes one second for Vanya. But if Vanya will enter wrong password k times, then he is able to make the next try only 5 seconds after that. Vanya makes each try immediately, that is, at each moment when Vanya is able to enter password, he is doing that.

Determine how many seconds will Vanya need to enter Codehorses in the best case for him (if he spends minimum possible number of second) and in the worst case (if he spends maximum possible amount of seconds).

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