Leetcode 696. Count Binary Substrings

class Solution:
    def countBinarySubstrings(self, s: str) -> int:
        length = len(s)
        count = 0
        pre = 0
        curr = 1
        for i in range(1, length):
            if s[i] == s[i - 1]:
                curr += 1
            else:
                count += min(pre, curr)
                pre = curr
                curr = 1
        count += min(pre, curr)
        return count