420. Strong Password Checker

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

class Solution(object):
    def strongPasswordChecker(self, s):
        """
        :type s: str
        :rtype: int
        """
        missing_type_cnt = 3
        if any('a' <= c <= 'z' for c in s):
            missing_type_cnt -= 1
        if any('A' <= c <= 'Z' for c in s):
            missing_type_cnt -= 1
        if any(c.isdigit() for c in s):
            missing_type_cnt -= 1

        total_change_cnt = 0
        one_change_cnt, two_change_cnt, three_change_cnt = 0, 0, 0
        i = 2
        while i < len(s):
            if s[i] == s[i-1] == s[i-2]:
                length = 2
                while i < len(s) and s[i] == s[i-1]:
                    length += 1
                    i += 1

                total_change_cnt += length / 3
                if length % 3 == 0:
                    one_change_cnt += 1
                elif length % 3 == 1:
                    two_change_cnt += 1
                else:
                    three_change_cnt += 1
            else:
                i += 1

        if len(s) < 6:
            return max(missing_type_cnt, 6 - len(s))
        elif len(s) <= 20:
            return max(missing_type_cnt, total_change_cnt)
        else:
            delete_cnt = len(s) - 20

            total_change_cnt -= min(delete_cnt, one_change_cnt * 1) / 1
            total_change_cnt -= min(max(delete_cnt - one_change_cnt, 0), two_change_cnt * 2) / 2
            total_change_cnt -= min(max(delete_cnt - one_change_cnt - 2 * two_change_cnt, 0), three_change_cnt * 3) / 3

            return delete_cnt + max(missing_type_cnt, total_change_cnt)

Solution from kamyu104/LeetCode-Solutions · MIT