strong-password-checker.py

# -*- coding:utf-8 -*-


# A password is considered strong if below conditions are all met:
#
#
#  It has at least 6 characters and at most 20 characters. 
#  It must contain at least one lowercase letter, at least one uppercase letter, and at least one digit. 
#  It must NOT contain three repeating characters in a row ("...aaa..." is weak, but "...aa...a..." is strong, assuming other conditions are met). 
#
#
# Write a function strongPasswordChecker(s), that takes a string s as input, and return the MINIMUM change required to make s a strong password. If s is already strong, return 0.
#
# Insertion, deletion or replace of any one character are all considered as one change.


class Solution(object):
    def strongPasswordChecker(self, s):
        """
        :type s: str
        :rtype: int
        """
        missing_type = 3
        if any(c.islower() for c in s): missing_type -= 1
        if any(c.isupper() for c in s): missing_type -= 1
        if any(c.isdigit() for c in s): missing_type -= 1

        change = 0
        one = two = 0
        p = 2
        while p < len(s):
            if s[p] == s[p-1] == s[p-2]:
                length = 2
                while p < len(s) and s[p] == s[p-1]:
                    length += 1
                    p += 1
                    
                change += length / 3
                if length % 3 == 0: one += 1
                elif length % 3 == 1: two += 1
            else:
                p += 1
        
        if len(s) < 6:
            return max(missing_type, 6 - len(s))
        elif len(s) <= 20:
            return max(missing_type, change)
        else:
            delete = len(s) - 20
            
            change -= min(delete, one)
            change -= min(max(delete - one, 0), two * 2) / 2
            change -= max(delete - one - 2 * two, 0) / 3
                
            return delete + max(missing_type, change)