LeetCode-LongestPalindromicSubstring

2019-11-14 14:51:38

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题目：

Given a string S, find the longest palindromic substring in S. You may assume that the maximum length of S is 1000, and there exists one unique longest palindromic substring.

思路：

以每个点为基础，寻找回文字符串，两种情况，一种是形如aba，中心店两边是对称的，长度为奇数，另一种是形如aa，长度为偶数。

package string;public class LongestPalindromicSubstring {    public String longestPalindrome(String s) {        int len = s.length();        String max = "";        for (int i = 0; i < len; ++i) {            String res = getStr(s, len, i, i);            if (res.length() > max.length())                max = res;            if (i + 1 < len && s.charAt(i) == s.charAt(i + 1)) {                res = getStr(s, len, i, i + 1);                if (res.length() > max.length())                    max = res;            }        }                return max;    }        PRivate String getStr(String s, int len, int left, int right) {        while (right < len && left >= 0 && s.charAt(left) == s.charAt(right)) {            --left;            ++right;        }        return s.substring(left + 1, right);    }            public static void main(String[] args) {        // TODO Auto-generated method stub        LongestPalindromicSubstring l = new LongestPalindromicSubstring();        System.out.println(l.longestPalindrome("aabbcc"));    }}