package com.fishercoder.solutions;

/**
 * Given a string s, find the longest palindromic substring in s. You may assume that the maximum length of s is 1000.

 Example:

 Input: "babad"

 Output: "bab"

 Note: "aba" is also a valid answer.
 Example:

 Input: "cbbd"

 Output: "bb"
 */
public class _5 {

    private int lo, maxLen;

    public String longestPalindrome(String s) {
        int len = s.length();
        if (len < 2)
            return s;

        for (int i = 0; i < len - 1; i++) {
            extendPalindrome(s, i, i); // assume odd length, try to extend Palindrome as possible
            extendPalindrome(s, i, i + 1); // assume even length.
        }
        return s.substring(lo, lo + maxLen);
    }

    private void extendPalindrome(String s, int j, int k) {
        while (j >= 0 && k < s.length() && s.charAt(j) == s.charAt(k)) {
            j--;
            k++;
        }
        if (maxLen < k - j - 1) {
            lo = j + 1;
            maxLen = k - j - 1;
        }
    }

}

package com.fishercoder.solutions;

/**
 * 5. Longest Palindromic Substring
 *
 * Given a string s, find the longest palindromic substring in s. You may assume that the maximum length of s is 1000.

 Example:
 Input: "babad"
 Output: "bab"
 Note: "aba" is also a valid answer.

 Example:
 Input: "cbbd"
 Output: "bb"
 */
public class _5 {

    private int low, maxLen;

    public String longestPalindrome(String s) {
        int len = s.length();
        if (len < 2) {
            return s;
        }

        for (int i = 0; i < len - 1; i++) {
            extendPalindrome(s, i, i); // assume odd length, try to extend Palindrome as possible
            extendPalindrome(s, i, i + 1); // assume even length.
        }
        return s.substring(low, low + maxLen);
    }

    private void extendPalindrome(String s, int left, int right) {
        while (left >= 0 && right < s.length() && s.charAt(left) == s.charAt(right)) {
            left--;
            right++;
        }
        if (maxLen < right - left - 1) {
            low = left + 1;
            maxLen = right - left - 1;
        }
    }

}

edit 5