强密码检验器 II【LC2299】

A password is said to be strong if it satisfies all the following criteria:

• It has at least 8 characters.
• It contains at least one lowercase letter.
• It contains at least one uppercase letter.
• It contains at least one digit.
• It contains at least one special character. The special characters are the characters in the following string: "!@#$%^&*()-+".
• It does not contain 2 of the same character in adjacent positions (i.e., "aab" violates this condition, but "aba" does not).

Given a string password, return true if it is a strong password. Otherwise, return false.

• 思路：首先判断密码长度是否大于等于8，若是则判断该密码是否包含至少一个数字、小写字母、大写字母以及特殊字符，并相邻字符不相同，若满足条件则返回true。

• 实现：使用一个变量记录该密码是否包含数字、小写字母、大写字母以及特殊字符，若都包含则返回true。

class Solution {
    public boolean strongPasswordCheckerII(String password) {
        int n = password.length();
        if (n < 8){
            return false;
        }
        int flag = 0;
        for (int i = 0; i < password.length(); i++){
            char c = password.charAt(i);
            if (i > 0 && password.charAt(i - 1) == c){
                return false;
            }
            if ( c >= '0' && c <= '9'){
                flag |= 1 << 0;
            }else if ( c >= 'a' && c <= 'z'){
                flag |= 1 << 1;
            }else if ( c >= 'A' && c <= 'Z'){
                flag |= 1 << 2;
            }else{
                flag |= 1 << 3;
            }
        }
        return flag >= 15;
    }
}

。复杂度分析

• 时间复杂度：O ( n )
• 空间复杂度：O ( 1 )