Maximize Number of Subsequences in a String — Python

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

# counting, greedy
class Solution(object):
    def maximumSubsequenceCount(self, text, pattern):
        """
        :type text: str
        :type pattern: str
        :rtype: int
        """
        result = cnt1 = cnt2 = 0
        for c in text:
            if c == pattern[1]:
                result += cnt1
                cnt2 += 1
            if c == pattern[0]:
                cnt1 += 1
        return result + max(cnt1, cnt2)  # add pattern[1] at back or pattern[0] at front