1573. Number of Ways to Split a String

https://leetcode.com/problems/number-of-ways-to-split-a-string

Description

Given a binary string s (a string consisting only of '0's and '1's), we can split s into 3 non-empty strings s1, s2, s3 (s1+ s2+ s3 = s).

Return the number of ways s can be split such that the number of characters '1' is the same in s1, s2, and s3.

Since the answer may be too large, return it modulo 10^9 + 7.

Example 1:

**Input:** s = "10101"
**Output:** 4
**Explanation:** There are four ways to split s in 3 parts where each part contain the same number of letters '1'.
"1|010|1"
"1|01|01"
"10|10|1"
"10|1|01"

Example 2:

**Input:** s = "1001"
**Output:** 0

Example 3:

**Input:** s = "0000"
**Output:** 3
**Explanation:** There are three ways to split s in 3 parts.
"0|0|00"
"0|00|0"
"00|0|0"

Example 4:

**Input:** s = "100100010100110"
**Output:** 12

Constraints:

• 3 <= s.length <= 10^5

• s[i] is '0' or '1'.

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