1573. Number of Ways to Split a String

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 109 + 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