Start by clarifying the problem constraints and edge cases, then propose a greedy algorithm that scans from the right to find the rightmost position where you can increment a character while maintaining the no-adjacent-equal property. After incrementing, fill the suffix with the smallest possible characters, ensuring no two adjacent characters are the same.
Pro tip: Demonstrate awareness of edge cases like when the input is already the largest possible string (e.g., all 'z's) and discuss the time complexity (O(n)) and space complexity (O(n) or O(1) if modifying in place).
Ask about the character set (e.g., lowercase letters), string length, and whether the input can be empty. Discuss edge cases like no valid string exists (e.g., 'zzz').
Scan from right to left to find the first character that can be incremented without violating the no-adjacent-equal rule with its left neighbor and while allowing a valid suffix.
Increment the character at that position, then fill the remaining positions with the smallest possible characters (e.g., 'a', 'b') ensuring no two adjacent characters are equal.
If no such position exists, return an empty string or indicate that no valid string exists, depending on the problem requirements.
State the time and space complexity, and walk through examples to verify correctness, including edge cases.
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