1573 - Number of Ways to Split a String.

Medium

Given a binary string s, you can split s into 3 non-empty strings s1, s2, and s3 where s1 + s2 + s3 = s.

Return the number of ways s can be split such that the number of ones is the same in s1, s2, and s3. Since the answer may be too large, return it modulo <code>10⁹ + 7</code>.

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"

Constraints:

• <code>3 <= s.length <= 10⁵</code>

• s[i] is either '0' or '1'.