A14796. Paint the Middle
编程题
普及/提高-
知识点
题目描述
You are given $n$ elements numbered from $1$ to $n$ , the element $i$ has value $a_i$ and color $c_i$ , initially, $c_i = 0$ for all $i$ .
The following operation can be applied:
- Select three elements $i$ , $j$ and $k$ ( $1 \leq i < j < k \leq n$ ), such that $c_i$ , $c_j$ and $c_k$ are all equal to $0$ and $a_i = a_k$ , then set $c_j = 1$ .
Find the maximum value of $\sum\limits_{i=1}^n{c_i}$ that can be obtained after applying the given operation any number of times.
The following operation can be applied:
- Select three elements $i$ , $j$ and $k$ ( $1 \leq i < j < k \leq n$ ), such that $c_i$ , $c_j$ and $c_k$ are all equal to $0$ and $a_i = a_k$ , then set $c_j = 1$ .
Find the maximum value of $\sum\limits_{i=1}^n{c_i}$ that can be obtained after applying the given operation any number of times.
输入格式
The first line contains an integer $n$ ( $3 \leq n \leq 2 \cdot 10^5$ ) — the number of elements.
The second line consists of $n$ integers $a_1, a_2, \dots, a_n$ ( $1 \leq a_i \leq n$ ), where $a_i$ is the value of the $i$ -th element.
The second line consists of $n$ integers $a_1, a_2, \dots, a_n$ ( $1 \leq a_i \leq n$ ), where $a_i$ is the value of the $i$ -th element.
输出格式
Print a single integer in a line — the maximum value of $\sum\limits_{i=1}^n{c_i}$ that can be obtained after applying the given operation any number of times.
输入输出样例
输入 #1
7 1 2 1 2 7 4 7
输出 #1
2
输入 #2
13 1 2 3 2 1 3 3 4 5 5 5 4 7
输出 #2
7
说明/提示
In the first test, it is possible to apply the following operations in order:
