Leetcode 5 Longest Palindromic Substring Java Solution
// SOLVING THIS WITH AN AI ASSISTANT (2026)
If you are working through this problem with an AI coding assistant — Claude, ChatGPT, Cursor chat, Gemini, GitHub Copilot, Aider, or any agent — the goal isn’t to ask for the answer. It is to use the tool to understand the pattern. The prompt sequence I’d run:
- Spec it back to me first. “In your own words, what is this problem actually testing? What’s the smallest example that fails the naive approach?”
- Brute-force first, optimize after. “Write the simplest correct solution, even if it’s O(n²). Don’t optimize. Just make it correct, with comments explaining each step.”
- Ask for the upgrade. “Now show me the optimal solution. What insight makes it possible? What pattern is this an instance of?”
- Stress-test it. “Generate 10 edge cases — empty input, single element, duplicates, max size, sorted, reverse-sorted. Run my solution against each.”
The pattern matters more than the answer. If the agent just hands you optimized code, you’ve trained yourself to lose interviews.
Given a string s, find the longest palindromic substring in s. You may assume that the maximum length of s is 1000.
Example 1:
Input: "babad" Output: "bab" Note: "aba" is also a valid answer.
Example 2:
Input: "cbbd" Output: "bb" Solution 1:
class Solution {
public String longestPalindrome(String s) {
if(s==null || s.length()<=1) return s;
boolean dp[][] = new boolean[s.length()][s.length()];
String longest = null;
int maxLength = 1;
int len = s.length();
for(int l=0; l<s.length(); l++){
for(int i=0; i<len-l; i++){
int j = i+l;
if(s.charAt(i)==s.charAt(j) && (j-i<=2||dp[i+1][j-1])){
dp[i][j]=true;
if(j-i+1>maxLength){
maxLength = j-i+1;
longest = s.substring(i, j+1);
}
}
}
}
if(longest == null) return s.substring(0,1);
return longest;
}
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