Number of Ways to Split a String LeetCode solution in Python

1
class Solution:
2
    def numWays(self, s: str) -> int:
3
        ones = 0
4

5
        # Count number of Ones
6
        for char in s:
7
            if char == "1":
8
                ones += 1
9

10
        # Can't be grouped equally if the ones are not divisible by 3
11
        if ones > 0 and ones % 3 != 0:
12
            return 0
13

14
        # Ways of selecting two dividers from n - 1 dividers
15
        if ones == 0:
16
            n = len(s)
17
            # n = {3: 1, 4: 3, 5: 6, 6: 10, 7: 15 ... }
18
            return (((n - 1) * (n - 2)) // 2) % ((10**9) + 7)
19

20
        # Number of ones in each group
21
        ones_interval = ones // 3
22

23
        # Number of zeroes which lie on the borders
24
        left, right = 0, 0
25

26
        # Iterator
27
        i = 0
28
        temp = 0
29

30
        # Finding the zeroes on the left and right border
31
        while i < len(s):
32
            temp += int(s[i]) & 1
33
            if temp == ones_interval:
34
                if s[i] == "0":
35
                    left += 1
36
            if temp == 2 * ones_interval:
37
                if s[i] == "0":
38
                    right += 1
39
            i += 1
40

41
        # The result is the product of number of (left + 1) and (right + 1)
42
        # Because let's assume it as we only want to fill up the middle group
43
        # The solution would be if we have zero then there might be a zero in the middle
44
        # Or there might not be the zero, so this might case is added and then
45
        # the events are independent so product of both the events
46
        return ((left + 1) * (right + 1)) % ((10**9) + 7)