No.1996 <><
タグ : / 解いたユーザー数 93
作問者 :
MasKoaTS
/ テスター :
👑 Problem Statement
You are given a sequence of positive integers $A = ( A_{1}, A_{2}, \dots, A_{N} )$ of length $N$ and a string $s$ of length $K$ consisting only of < and >.
Below, the $i$-th $(1 \leq i \leq K)$ character from the beginning of $s$ is denoted by $s_{i}$.
Find the number of ways to choose a tuple of integers $(x_{1}, x_{2}, \dots, x_{K+1})$ satisfying $1 \leq x_{1} < x_{2} < \cdots < x_{K+1} \leq N$
such that,
for all $i = 1, 2, \dots, K$, both of the following $2$ conditions hold.
If $s_{i}$ is
<, then $A_{x_{i} } < A_{x_{i+1} }$.If $s_{i}$ is
>, then $A_{x_{i} } > A_{x_{i+1} }$.
Since the answer can be very large, print the remainder when it is divided by $10^{9}+7$.
Constraints
$1 \leq K < N \leq 1500$
$1 \leq A_{i} \leq 10^{9}$ $(1 \leq i \leq N)$
$N$, $K$, and $A_{i}$ $(1 \leq i \leq N)$ are all integers.
$s$ is a string of length $K$ consisting only of
<and>.
Input
The input is given in the following format.
$N$ $K$
$A_{1}$ $A_{2}$ $\cdots$ $A_{N}$
$s$
Line $1$ contains $N$, $K$ in this order, separated by half-width spaces.
Line $2$ contains $A_{1}, A_{2}, \dots, A_{N}$ in this order, separated by half-width spaces.
Line $3$ contains $s$.
Output
Print the answer on $1$ line, followed by a newline.
Sample
Sample 1
Input
5 3 2 3 1 1 4 <><
Output
2
The tuples satisfying the conditions are $(x_{1}, x_{2}, x_{3}, x_{4}) = (1,2,3,5), (1,2,4,5)$, for a total of $2$.
For example, when $(x_{1}, x_{2}, x_{3}, x_{4}) = (1,2,4,5)$, $(A_{1}, A_{2}, A_{4}, A_{5} ) = (2,3,1,4)$ satisfies all of the $3$ inequalities
$2 < 3$
$3 > 1$
$1 < 4$
Sample 2
Input
6 4 1 1 2 5 1 4 >><<
Output
0
No tuple of integers satisfies the conditions.
Sample 3
Input
20 5 13359410 197769 10910581 3 512 5732 9026607 22294 3997084 262110309 51421 728930621 353629015 49 1907 208452 13 13760365 6779710 3484117 ><><<
Output
1744
Sample 4
Input
40 19 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 <<<<<<<<<<<<<<<<<<<
Output
846527861
Print the remainder when the number of tuples of integers satisfying the conditions is divided by $10^{9} + 7$.
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