LeetCode 5. Longest Palindromic Substring(字符串)

• By Scarb
• Scarb’s Blog

Tags:
- String

问题描述

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"

解题思路

遍历字符串的每一位，对每一位从中间展开，寻找该位(或者该位和下一位相同的情况就找该位和下一位)为中心的最长回文字符串。

参考代码

#include <iostream>#include <string>#include <algorithm>using namespace std;class Solution {public:    string longestPalindrome(string s) {        int start = 0, end = 0;        for (int i = 0; i < s.length(); ++i)        {            int len1 = expandFromCenter(s, i, i);            int len2 = expandFromCenter(s, i, i + 1);            int len = max(len1, len2);            if(len > end - start + 1)            {                start = i - (len - 1) / 2;                end = i + len / 2;            }        }        return s.substr(start, end - start + 1);    }private:    int expandFromCenter(string s, int left, int right)    {        int L = left, R = right;        while (L >= 0 && R < s.length() && s[L] == s[R])        {            --L;            ++R;        }        return R - L + 1 - 2;    }};int main(){    string test = "babad";    auto sl = new Solution();    cout << sl->longestPalindrome(test) << endl;    system("pause");    return 0;}