minimum-deletions-to-make-string-balanced.py

# Time:  O(n)
# Space: O(1)

class Solution(object):
    def minimumDeletions(self, s):
        """
        :type s: str
        :rtype: int
        """
        result = b_cnt = 0
        for c in s:
            if c == 'b':
                b_cnt += 1
            elif b_cnt:
                b_cnt -= 1
                result += 1
        return result