Codeforces Round 700 (Div. 1)
B2
Painting the Array II
Codeforces
2100
原题
← B1C →
翻译中…

The only difference between the two versions is that this version asks the minimal possible answer.

翻译中…

Homer likes arrays a lot. Today he is painting an array $a_1, a_2, \dots, a_n$ with two kinds of colors, white and black. A painting assignment for $a_1, a_2, \dots, a_n$ is described by an array $b_1, b_2, \dots, b_n$ that $b_i$ indicates the color of $a_i$ ($0$ for white and $1$ for black).

翻译中…

According to a painting assignment $b_1, b_2, \dots, b_n$, the array $a$ is split into two new arrays $a^{(0)}$ and $a^{(1)}$, where $a^{(0)}$ is the sub-sequence of all white elements in $a$ and $a^{(1)}$ is the sub-sequence of all black elements in $a$. For example, if $a = [1,2,3,4,5,6]$ and $b = [0,1,0,1,0,0]$, then $a^{(0)} = [1,3,5,6]$ and $a^{(1)} = [2,4]$.

翻译中…

The number of segments in an array $c_1, c_2, \dots, c_k$, denoted $\mathit{seg}(c)$, is the number of elements if we merge all adjacent elements with the same value in $c$. For example, the number of segments in $[1,1,2,2,3,3,3,2]$ is $4$, because the array will become $[1,2,3,2]$ after merging adjacent elements with the same value. Especially, the number of segments in an empty array is $0$.

翻译中…

Homer wants to find a painting assignment $b$, according to which the number of segments in both $a^{(0)}$ and $a^{(1)}$, i.e. $\mathit{seg}(a^{(0)})+\mathit{seg}(a^{(1)})$, is as small as possible. Find this number.

翻译中…

Input

翻译中…

The first line contains an integer $n$ ($1 \leq n \leq 10^5$).

翻译中…

The second line contains $n$ integers $a_1, a_2, \dots, a_n$ ($1 \leq a_i \leq n$).

翻译中…

Output

翻译中…

Output a single integer, indicating the minimal possible total number of segments.

翻译中…

Note

翻译中…

In the first example, we can choose $a^{(0)} = [1,1,2,2]$, $a^{(1)} = [2,3]$ and $\mathit{seg}(a^{(0)}) = \mathit{seg}(a^{(1)}) = 2$. So the answer is $2+2 = 4$.

翻译中…

In the second example, we can choose $a^{(0)} = [1,1,1,1]$, $a^{(1)} = [2,2,2]$ and $\mathit{seg}(a^{(0)}) = \mathit{seg}(a^{(1)}) = 1$. So the answer is $1+1 = 2$.

翻译中…

样例

Input #1
6
1 2 3 1 2 2
Output #1
4
InputCopy OutputCopy
Input #2
7
1 2 1 2 1 2 1
Output #2
2
InputCopy OutputCopy
题目信息
题号
1479B2
时间限制
2 s
内存限制
512 MB
标签
构造
数据结构
动态规划
贪心
模拟

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。