Preparando MOJI
Mr. Chanek gives you a sequence $$$a$$$ indexed from $$$1$$$ to $$$n$$$. Define $$$f(a)$$$ as the number of indices where $$$a_i = i$$$.
You can pick an element from the current sequence and remove it, then concatenate the remaining elements together. For example, if you remove the $$$3$$$-rd element from the sequence $$$[4, 2, 3, 1]$$$, the resulting sequence will be $$$[4, 2, 1]$$$.
You want to remove some elements from $$$a$$$ in order to maximize $$$f(a)$$$, using zero or more operations. Find the largest possible $$$f(a)$$$.
The first line contains one integer $$$n$$$ ($$$1 \leq n \leq 2 \cdot 10^5$$$) — the initial length of the sequence.
The second line contains $$$n$$$ integers $$$a_1, a_2, \ldots, a_n$$$ ($$$1 \leq a_i \leq 2 \cdot 10^5$$$) — the initial sequence $$$a$$$.
Output an integer denoting the largest $$$f(a)$$$ that can be obtained by doing zero or more operations.
7 2 1 4 2 5 3 7
3
4 4 2 3 1
2
In the first example, $$$f(A) = 3$$$ by doing the following operations.
$$$[2,1,\textbf{4},2,5,3,7] \rightarrow [\textbf{2},1,2,5,3,7] \rightarrow [1,2,5,3,\textbf{7}] \rightarrow [1,2,\textbf{5},3] \rightarrow [1,2,3]$$$
In the second example, $$$f(A) = 2$$$ and no additional operation is needed.
Informação
Provedor Codeforces
Código CF1575L
Tags
Submetido 0
BOUA! 0
Taxa de BOUA's 0%
Datas 09/05/2023 10:17:56
Relacionados