LeetCode-5*(回文)

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"

class Solution {
public:
string longestPalindrome(string s) {
if(s.empty())  return "";  //空串
if(s.size() == 1)  return s;  //单字符串
int start = 0, len = 1;  //回文子串开始,长度
for(int i = 0;i<s.size();){
if(s.size()-i <= len/2)  break;
int j = i, k = i;
while(k<s.size()-1 && s[k] == s[k+1])  k++;  //掠过重复字符
i = k+1;   //i存储回文子串对称轴心,如有重复字符的话,指向重复字符的后一个

while(k<s.size()-1 && j>0 && s[k+1]==s[j-1])  { k++;  j--; }
int newlen=k-j+1;
if(newlen>len){
len = newlen;
start = j;
}
}
return s.substr(start,len);
}
};

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