Good Bye 2020
G
Song of the Sirens
Codeforces
2600
原题
← FH →
翻译中…

*Whoso in ignorance draws near to them and hears the Sirens' voice, he nevermore returns.*Homer, Odyssey

翻译中…

In the times of Jason and the Argonauts, it was well known that sirens use the sound of their songs to lure sailors into their demise. Yet only a few knew that every time sirens call a sailor by his name, his will weakens, making him more vulnerable.

翻译中…

For the purpose of this problem, both siren songs and names of the sailors will be represented as strings of lowercase English letters. The more times the sailor's name occurs as a contiguous substring of the song, the greater danger he is in.

翻译中…

Jason found out that sirens can sing one of the $n+1$ songs, which have the following structure: let $s_i$ ($0 \leq i \leq n$) be the $i$-th song and $t$ be a string of length $n$, then for every $i \lt n$: $s_{i+1} = s_i t_i s_i$. In other words $i+1$-st song is the concatenation of $i$-th song, $i$-th letter ($0$-indexed) of $t$ and the $i$-th song.

翻译中…

Fortunately, he also knows $s_0$ and $t$. Jason wonders how many times a sailor's name is mentioned in a particular song. Answer $q$ queries: given the sailor's name ($w$) and the index of a song ($i$) output the number of occurrences of $w$ in $s_i$ as a substring. As this number can be quite large, output its remainder modulo $10^9+7$.

翻译中…

Input

翻译中…

In the first line of input there are two integers $n$, $q$ ( $ 1 \leq n, q \leq 10^5$) meaning that there are $n+1$ songs and $q$ queries. In the next two lines strings $s_0$ and $t$ follow ($1 \leq |s_0| \leq 100, |t| = n$).

翻译中…

Next $q$ lines describe the queries; each one contains an integer $k$ ($ 0 \leq k \leq n$), the index of the song sung by the sirens, and a non-empty string $w$, which is the name of a sailor. All strings in this problem consist only of lowercase English letters, and the sum of lengths of sailors' names does not exceed $10^6$.

翻译中…

Output

翻译中…

Output $q$ lines, $i$-th of them should contain the remainder modulo $10^9+7$ of the number of occurrences of $w$ in $s_k$.

翻译中…

Note

翻译中…

In the first example songs of the sirens are as follows:

翻译中…
  • Song $0$: aa
  • Song $1$: aabaa
  • Song $2$: aabaacaabaa
  • Song $3$: aabaacaabaadaabaacaabaa
翻译中…

样例

Input #1
3 3
aa
bcd
2 aba
3 ca
3 aa
Output #1
2
2
8
InputCopy OutputCopy
Input #2
4 5
aba
bbac
1 a
3 baca
3 ab
2 bab
4 aba
Output #2
4
0
14
6
28
InputCopy OutputCopy
题目信息
题号
1466G
所属比赛
时间限制
2 s
内存限制
256 MB
标签
组合数学
分治
哈希
数学
后缀结构
字符串

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。