Codeforces Round 659 (Div. 1)
E
Strange Operation
Codeforces
2800
原题
← DF →
翻译中…

Koa the Koala has a binary string $s$ of length $n$. Koa can perform no more than $n-1$ (possibly zero) operations of the following form:

翻译中…

In one operation Koa selects positions $i$ and $i+1$ for some $i$ with $1 \le i \lt |s|$ and sets $s_i$ to $max(s_i, s_{i+1})$. Then Koa deletes position $i+1$ from $s$ (after the removal, the remaining parts are concatenated).

翻译中…

Note that after every operation the length of $s$ decreases by $1$.

翻译中…

How many different binary strings can Koa obtain by doing no more than $n-1$ (possibly zero) operations modulo $10^9+7$ ($1000000007$)?

翻译中…

Input

翻译中…

The only line of input contains binary string $s$ ($1 \le |s| \le 10^6$). For all $i$ ($1 \le i \le |s|$) $s_i = 0$ or $s_i = 1$.

翻译中…

Output

翻译中…

On a single line print the answer to the problem modulo $10^9+7$ ($1000000007$).

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Note

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In the first sample Koa can obtain binary strings: $0$, $00$ and $000$.

翻译中…

In the second sample Koa can obtain binary strings: $1$, $01$, $11$, $011$, $101$ and $0101$. For example:

翻译中…
  • to obtain $01$ from $0101$ Koa can operate as follows: $0101 \rightarrow 0(10)1 \rightarrow 011 \rightarrow 0(11) \rightarrow 01$.
  • to obtain $11$ from $0101$ Koa can operate as follows: $0101 \rightarrow (01)01 \rightarrow 101 \rightarrow 1(01) \rightarrow 11$.
翻译中…

Parentheses denote the two positions Koa selected in each operation.

翻译中…

样例

Input #1
000
Output #1
3
InputCopy OutputCopy
Input #2
0101
Output #2
6
InputCopy OutputCopy
Input #3
0001111
Output #3
16
InputCopy OutputCopy
Input #4
00101100011100
Output #4
477
InputCopy OutputCopy
题目信息
题号
1383E
时间限制
1 s
内存限制
256 MB
标签
组合数学
数据结构
动态规划

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。