Interview Pro Tip
Red Flag: Forgetting to handle non-alphanumeric or case. Pro-Move: 'I ask about edge cases first: empty string, unicode, case. I implement two-pointer for O(1) space and mention when string concat would be simpler.'
**Approach**: Normalize (lowercase, alphanumeric only) and compare with reverse. **Code**: `def is_palindrome(s): cleaned = "".join(c.lower() for c in s if c.isalnum()); return cleaned == cleaned[::-1]`. **Two-pointer** (O(1) space, early exit): `lo, hi = 0, len(s)-1; while lo < hi: ... if not s[lo].isalnum(): lo+=1; continue; ... if s[lo].lower() != s[hi].lower(): return False; lo, hi = lo+1, hi-1; return True`. **Clarify**: Case sensitivity? Non-alphanumeric? Empty string (usually True)....
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