What is the approach to find the longest palindromic substring?
Finding the longest palindrome within a string is a common string manipulation challenge requiring expansion around centers or dynamic programming.
Why Interviewers Ask This
This problem tests string processing skills and the ability to handle even and odd length palindromes. Interviewers look for an understanding of expanding around centers or dynamic programming states. It evaluates attention to detail in boundary conditions and character comparisons.
How to Answer This Question
Explain the expand-around-center strategy where you treat each character (and gap between characters) as a potential center. Describe how to expand outward while characters match. Compare this with the dynamic programming approach which fills a table of palindrome status. Highlight the time complexity differences and why expansion is often preferred for simplicity.
Key Points to Cover
- Expand around centers
- Handle odd and even lengths
- Track longest valid range
- O(n^2) time complexity
Sample Answer
A robust approach is to expand around each possible center. Since a palindrome can be odd or even length, we check every character and every gap between characters as centers. For each center, we expand left and right as…
Common Mistakes to Avoid
- Missing even-length palindromes
- Incorrect boundary checks
- Using inefficient nested loops without pruning
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