count-binary-substrings.py

class Solution:
    def countBinarySubstrings(self, s):
        """
        :type s: str
        :rtype: int
        """
        ans, prev, cur = 0, 0, 1
        for i in range(1, len(s)):
            if s[i - 1] != s[i]:
                ans += min(cur, prev)
                prev, cur = cur, 1
            else:
                cur += 1
        return ans + min(cur, prev)