C. Sequence Transformation

最新推荐文章于 2022-07-14 19:56:12 发布

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最新推荐文章于 2022-07-14 19:56:12 发布 · 635 阅读

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给定一个初始包含 n 个整数的序列 a，你需要将其转化为所有元素都相等的序列。选择序列中至少出现一次的整数 x，然后可以任意次数地选择一段不包含 x 的子序列并删除。求达到目标所需的最小操作数。

https://codeforces.ml/contest/1454/problem/C

You are given a sequence aa, initially consisting of nn integers.

You want to transform this sequence so that all elements in it are equal (i. e. it contains several occurrences of the same element).

To achieve this, you choose some integer xx that occurs at least once in aa, and then perform the following operation any number of times (possibly zero): choose some segment [l,r][l,r] of the sequence and remove it. But there is one exception: you are not allowed to choose a segment that contains xx. More formally, you choose some contiguous subsequence [al,al+1,…,ar][al,al+1,…,ar] such that ai≠xai≠x if l≤i≤rl≤i≤r, and remove it. After removal, the numbering of elements to the right of the removed segment changes: the element that was the (r+1)(r+1)-th