#P6155. Subsequence Count
Subsequence Count
Problem Description
Given a binary string $S[1,...,N]$ (i.e. a sequence of 0's and 1's), and $Q$ queries on the string.
There are two types of queries:
1. Flipping the bits (i.e., changing all 1 to 0 and 0 to 1) between $l$ and $r$ (inclusive).
2. Counting the number of distinct subsequences in the substring $S[l,...,r]$.
Input
The first line contains an integer $T$, denoting the number of the test cases.
For each test, the first line contains two integers $N$ and $Q$.
The second line contains the string $S$.
Then $Q$ lines follow, each with three integers $type$, $l$ and $r$, denoting the queries.
$1\leq T\leq 5$
$1\leq N, Q\leq 10^5$
$S[i]\in \lbrace 0, 1 \rbrace, \forall 1\leq i\leq N$
$type\in \lbrace 1, 2 \rbrace$
$1\leq l \leq r\leq N$
Output
For each query of type 2, output the answer mod ($10^9+7$) in one line.
2
4 4
1010
2 1 4
2 2 4
1 2 3
2 1 4
4 4
0000
1 1 2
1 2 3
1 3 4
2 1 4
11
6
8
10