[leetcode] 5. 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.
Example:
Input: "cbbd" Output: "bb"
思路很简单:遍历字符串,找出以每个字符为中间字符的最长的回文串,再次遍历字符,找出以两个重复字符为中间字符的最长的字符串,从而得到字符串 s 的最长回文子串。
以下是我的代码,其中再确认中间字符时寻找最长回文串的代码重复了两次,也可以独立出一个函数来调用:
class Solution { public: string longestPalindrome(string s) { int pos = 0, left = 0, right = 0, len = s.size(); string result = ""; while (pos < len) { while (1) { if (s[left] != s[right]) break; string tmp = s.substr(left, right - left + 1); if (tmp.size() > result.size()) result = tmp; if (--left < 0) break; if (++right >= len) break; } pos++; left = pos, right = pos; } for (int i = 0; i < len - 1; i++) { if (s[i] == s[i+1]) { left = i, right = i+1; while (1) { if (s[left] != s[right]) break; string tmp = s.substr(left, right - left + 1); if (tmp.size() > result.size()) result = tmp; if (--left < 0) break; if (++right >= len) break; } } } return result; } };