5. Longest Palindromic Substring

最新推荐文章于 2024-01-20 11:35:01 发布

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最新推荐文章于 2024-01-20 11:35:01 发布

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本文介绍了一种高效算法来找出给定字符串中的最长回文子串。通过中心扩展法，该算法能处理各种长度的回文串，适用于最大长度为1000的字符串，并确保找到唯一最长的回文子串。

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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.

class Solution {
		public:

		    string expandAroundCenter(string s, int c1, int c2) {
		  int l = c1, r = c2;
		  int n = s.length();
		  while (l >= 0 && r <= n-1 && s[l] == s[r]) {
		    l--;
		    r++;
		  }
		  return s.substr(l+1, r-l-1);
		}
		 
		string longestPalindrome(string s) {
		  int n = s.length();
		  if (n == 0) return "";
		  string longest = s.substr(0, 1);  // a single char itself is a palindrome
		  for (int i = 0; i < n-1; i++) {
		    string p1 = expandAroundCenter(s, i, i);
		    if (p1.length() > longest.length())
		      longest = p1;
		 
		    string p2 = expandAroundCenter(s, i, i+1);
		    if (p2.length() > longest.length())
		      longest = p2;
		  }
		  return longest;
		}
		};