leetcode 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.

题意：找到字符串s中最长回文子串

class Solution {
public:
string longestPalindrome(string s) {
//处理边界情况
if (s.empty()) return "";
if (s.length() == 1) return s;
int min_start = 0, max_len = 1;
for (int i = 0; i < s.length();) {
if (s.length() - i <= max_len / 2) break;
int j = i, k = i;
while (k < s.length()-1 && s[k+1] == s[k]) ++k;//跳过相同字符
i = k + 1;
while (k < s.length()-1 && j > 0 && s[k+1] == s[j-1]) {
++k;
--j;
}//左右扩张
int new_len = k - j + 1;
if (new_len > max_len) {
min_start = j;
max_len = new_len;
}
}
return s.substr(min_start, max_len);
}
};