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原题：

/** * Created by gouthamvidyapradhan on 24/02/2017. * Given a string s, find the longest palindromic substring in s. You may assume that the maximum length of s is 1000. * <p> * Example: * <p> * Input: "babad" * <p> * Output: "bab" * <p> * Note: "aba" is also a valid answer. * Example: * <p> * Input: "cbbd" * <p> * Output: "bb" */

答案：

public class LongestPaliandromicSubstring {    /**     * Main method     *     * @param args     * @throws Exception     */    public static void main(String[] args) throws Exception {        System.out.println(new LongestPaliandromicSubstring().longestPalindrome("forgeeksskeegfor"));    }    public String longestPalindrome(String s) {        int l = s.length();        int startIndex = 0;        int maxLen = 1;        boolean[][] A = new boolean[l][l];        for (int i = 0, j = 0; i < l; i++, j++)            A[i][j] = true;        for (int i = 0, j = i + 1; j < l; i++, j++) {            if (s.charAt(i) == s.charAt(j)) {                A[i][j] = true;                startIndex = i;                maxLen = 2;            }        }        for (int k = 3; k <= l; k++) {            for (int i = 0, j = k - 1; j < l; i++, j++) {                if (s.charAt(i) == s.charAt(j)) {                    A[i][j] = A[i + 1][j - 1];                    if (A[i][j]) {                        if (k > maxLen) {                            startIndex = i;                            maxLen = k;                        }                    }                }            }        }        return s.substring(startIndex, startIndex + maxLen);    }}

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