QOJ.ac

QOJ

時間限制: 7.0 s 記憶體限制: 1024 MB 總分: 100 可 Hack ✓

#10733. 波状寻找

统计

在本题中,给定两个固定参数 $k$ 和 $W$。

我们称一个长度为 $2k$ 的序列 $a_1, a_2, \dots, a_{2k}$ 为 shaky,当且仅当满足: $$\sum_{i=1}^{k} (k - i + 1)(a_i + a_{2k-i+1}) \geq W$$

我们称一个序列 $b_1, b_2, \dots, b_m$ 为 wavelike,当且仅当: $m \geq 2k$。 它至少包含一个 shaky 子序列。注意,该 shaky 子序列不需要是连续的。

给定一个序列 $s_1, s_2, \dots, s_n$,请从中选出尽可能多的互不相交的 wavelike 连续子序列。注意,选出的连续子序列不需要覆盖整个序列。这里,“连续子序列”指它必须是连续的(即子串)。

输入格式

第一行包含三个整数 $n, k$ 和 $W$ ($2 \leq n \leq 2 \cdot 10^5, 1 \leq k \leq \frac{n}{2}, |W| \leq 10^{17}$)。 第二行包含 $n$ 个整数 $s_1, s_2, \dots, s_n$ ($|s_i| \leq 10^6$)。

输出格式

输出一行一个整数,表示能够选出的互不相交的 wavelike 连续子序列的最大数量。

样例

样例输入 1

9 2 25
6 4 3 5 7 1 2 5 8

样例输出 1

2

样例输入 2

9 2 30
6 4 3 5 7 1 2 5 8

样例输出 2

1

样例输入 3

2 1 1
0 0

样例输出 3

0

样例输入 4

2 1 -6
-1 -5

样例输出 4

1

Discussions

About Discussions

The discussion section is only for posting: General Discussions (problem-solving strategies, alternative approaches), and Off-topic conversations.

This is NOT for reporting issues! If you want to report bugs or errors, please use the Issues section below.

Open Discussions 0
No discussions in this category.

Issues

About Issues

If you find any issues with the problem (statement, scoring, time/memory limits, test cases, etc.), you may submit an issue here. A problem moderator will review your issue.

Guidelines:

  1. This is not a place to publish discussions, editorials, or requests to debug your code. Issues are only visible to you and problem moderators.
  2. Do not submit duplicated issues.
  3. Issues must be filed in English or Chinese only.
Active Issues 0
No issues in this category.
Closed/Resolved Issues 0
No issues in this category.