1573. Number of Ways to Split a String

class Solution:
    def numWays(self, s: str) -> int:
        def find(x):
            t = 0
            for i, c in enumerate(s):
                t += int(c == '1')
                if t == x:
                    return i

        cnt, m = divmod(sum(c == '1' for c in s), 3)
        if m:
            return 0
        n = len(s)
        mod = 10**9 + 7
        if cnt == 0:
            return ((n - 1) * (n - 2) // 2) % mod
        i1, i2 = find(cnt), find(cnt + 1)
        j1, j2 = find(cnt * 2), find(cnt * 2 + 1)
        return (i2 - i1) * (j2 - j1) % (10**9 + 7)