Number of ways to split a string

class Solution:
    def numWays(self, s: str) -> int:
        ones = s.count("1")
        MOD = 10 ** 9 + 7
        if ones % 3 != 0:
            return 0
        if ones == 0:
            return ((len(s) - 1) * (len(s) - 2)) // 2  % MOD

        count = ones // 3

        left = 0
        left_count = 0
        right = len(s) - 1
        right_count = 0

        while left_count < count:
            if s[left] == '1':
                left_count += 1
            left += 1

        while right_count < count:
            if s[right] == '1':
                right_count += 1
            right -= 1

        left_zeros = 0
        while s[right] != '1':
            left_zeros += 1
            right -= 1

        right_zeros = 0
        while s[left] != '1':
            right_zeros += 1
            left += 1

        return (left_zeros + 1) * (right_zeros + 1)  % MOD

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 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:

3 <= s.length <= 10⁵
s[i] is either '0' or '1'.