Codeforces Round 669 (Div. 2)
D
Discrete Centrifugal Jumps
Codeforces
2200
原题
← CE →
翻译中…

There are $n$ beautiful skyscrapers in New York, the height of the $i$-th one is $h_i$. Today some villains have set on fire first $n - 1$ of them, and now the only safety building is $n$-th skyscraper.

翻译中…

Let's call a jump from $i$-th skyscraper to $j$-th ($i \lt j$) discrete, if all skyscrapers between are strictly lower or higher than both of them. Formally, jump is discrete, if $i \lt j$ and one of the following conditions satisfied:

翻译中…
  • $i + 1 = j$
  • $\max(h_{i + 1}, \ldots, h_{j - 1}) \lt \min(h_i, h_j)$
  • $\max(h_i, h_j) \lt \min(h_{i + 1}, \ldots, h_{j - 1})$.
翻译中…

At the moment, Vasya is staying on the first skyscraper and wants to live a little longer, so his goal is to reach $n$-th skyscraper with minimal count of discrete jumps. Help him with calcualting this number.

翻译中…

Input

翻译中…

The first line contains a single integer $n$ ($2 \le n \le 3 \cdot 10^5$) — total amount of skyscrapers.

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The second line contains $n$ integers $h_1, h_2, \ldots, h_n$ ($1 \le h_i \le 10^9$) — heights of skyscrapers.

翻译中…

Output

翻译中…

Print single number $k$ — minimal amount of discrete jumps. We can show that an answer always exists.

翻译中…

Note

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In the first testcase, Vasya can jump in the following way: $1 \rightarrow 2 \rightarrow 4 \rightarrow 5$.

翻译中…

In the second and third testcases, we can reach last skyscraper in one jump.

翻译中…

Sequence of jumps in the fourth testcase: $1 \rightarrow 3 \rightarrow 5$.

翻译中…

样例

Input #1
5
1 3 1 4 5
Output #1
3
InputCopy OutputCopy
Input #2
4
4 2 2 4
Output #2
1
InputCopy OutputCopy
Input #3
2
1 1
Output #3
1
InputCopy OutputCopy
Input #4
5
100 1 100 1 100
Output #4
2
InputCopy OutputCopy
题目信息
题号
1407D
时间限制
2 s
内存限制
256 MB
标签
数据结构
动态规划
图论

题面与样例版权归 Codeforces 及出题人所有;中文翻译由 AI 生成(CI 管线),如有出入请以原文为准。