Solution Explanation for Strong Password Checker II

This problem requires checking if a given password meets several criteria: length (at least 8 characters), presence of lowercase, uppercase, digit, and special characters, and the absence of consecutive repeating characters. The solution uses bit manipulation for efficient character type tracking.

Approach

The core idea is to use a bitmask to track the presence of different character types. Each bit in the mask represents a character type:

• Bit 0: Special character (!@#$%^&*()-+)
• Bit 1: Lowercase letter
• Bit 2: Uppercase letter
• Bit 3: Digit

The algorithm iterates through the password string:

1. Length Check: First, it verifies if the password's length is less than 8. If so, it immediately returns false.

2. Consecutive Character Check: During the iteration, it compares each character with the preceding one. If they are identical, it indicates consecutive repetition, and the function returns false.

3. Character Type Check: For each character, it checks its type (lowercase, uppercase, digit, or special character) and sets the corresponding bit in the mask accordingly.

4. Final Check: After iterating through the entire password, the algorithm checks if the mask is equal to 15 (binary 1111). This signifies the presence of all four required character types. If the mask is 15, the function returns true; otherwise, it returns false.

Time and Space Complexity Analysis

• Time Complexity: O(n), where n is the length of the password string. The algorithm iterates through the string once.

• Space Complexity: O(1). The algorithm uses a constant amount of extra space to store the mask variable, regardless of the input string's length.

Code Implementation (Python)

class Solution:
    def strongPasswordCheckerII(self, password: str) -> bool:
        if len(password) < 8:
            return False
        mask = 0
        for i, c in enumerate(password):
            if i and c == password[i - 1]:
                return False
            if c.islower():
                mask |= 1
            elif c.isupper():
                mask |= 2
            elif c.isdigit():
                mask |= 4
            else:
                mask |= 8
        return mask == 15
 

The code in other languages (Java, C++, Go, TypeScript, Rust, C) follows a very similar structure, adapting syntax and standard library functions appropriately. The core logic of bit manipulation and character type checking remains consistent across all implementations.