103355: [Atcoder]ABC335 F - Hop Sugoroku
Description
Score : $525$ points
Problem Statement
There is a row of $N$ squares labeled $1,2,\dots,N$ and a sequence $A=(A_1,A_2,\dots,A_N)$ of length $N$.
Initially, square $1$ is painted black, the other $N-1$ squares are painted white, and a piece is placed on square $1$.
You may repeat the following operation any number of times, possibly zero:
- When the piece is on square $i$, choose a positive integer $x$ and move the piece to square $i + A_i \times x$.
- Here, you cannot make a move with $i + A_i \times x > N$.
- Then, paint the square $i + A_i \times x$ black.
Find the number of possible sets of squares that can be painted black at the end of the operations, modulo $998244353$.
Constraints
- All input values are integers.
- $1 \le N \le 2 \times 10^5$
- $1 \le A_i \le 2 \times 10^5$
Input
The input is given from Standard Input in the following format:
$N$ $A_1$ $A_2$ $\dots$ $A_N$
Output
Print the answer as an integer.
Sample Input 1
5 1 2 3 1 1
Sample Output 1
8
There are eight possible sets of squares painted black:
- Square $1$
- Squares $1,2$
- Squares $1,2,4$
- Squares $1,2,4,5$
- Squares $1,3$
- Squares $1,4$
- Squares $1,4,5$
- Squares $1,5$
Sample Input 2
1 200000
Sample Output 2
1
Sample Input 3
40 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
Sample Output 3
721419738
Be sure to find the number modulo $998244353$.
Input
Output
问题描述
有一排标号为$1,2,\dots,N$的方格和一个长度为$N$的序列$A=(A_1,A_2,\dots,A_N)$。
最初,方格$1$被涂成黑色,其他$N-1$个方格被涂成白色,且在方格$1$上放置了一个棋子。
你可以重复执行任意多次(包括零次)以下操作:
- 当棋子在方格$i$上时,选择一个正整数$x$,将棋子移动到方格$i + A_i \times x$。
- 在这里,你不能进行移动使得$i + A_i \times x > N$。
- 然后,将方格$i + A_i \times x$涂成黑色。
找出在操作结束时,可能被涂成黑色的方格集合的数量,对$998244353$取模。
限制条件
- 所有输入值均为整数。
- $1 \le N \le 2 \times 10^5$
- $1 \le A_i \le 2 \times 10^5$
输入
输入将以标准输入的以下格式给出:
$N$ $A_1$ $A_2$ $\dots$ $A_N$
输出
打印答案作为整数。
样例输入 1
5 1 2 3 1 1
样例输出 1
8
有八种可能的方格被涂成黑色的集合:
- 方格$1$
- 方格$1,2$
- 方格$1,2,4$
- 方格$1,2,4,5$
- 方格$1,3$
- 方格$1,4$
- 方格$1,4,5$
- 方格$1,5$
样例输入 2
1 200000
样例输出 2
1
样例输入 3
40 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
样例输出 3
721419738
一定要对$998244353$取模。