Java [Leetcode 5] Longest palindromic Substring

Problem Description:

Given a string S, find the longest palindromic substring in s. The maximum length of S is assume, and there exists one unique longest palindromic substring.

Problem Solving Ideas:

Traversal method with a time complexity of O (n). It starts from the beginning of the string, and then spreads from the position to the sides in each traversal until the longest sub-palindrome is found. You also need to consider the case of odd and even strings.

The code is as follows:

1  Public classSolution {2     Publicstring Longestpalindrome (string s) {3         intn =s.length ();4String longest = s.substring (0, 1);5 6         if(s = =NULL|| S.length () = = 0)7             return NULL;8          for(inti = 0; I < n; i++) {9String P1 =Expandfromcenter (S, I, I);Ten             if(P1.length () >longest.length ()) OneLongest =P1; AString P2 = expandfromcenter (s, I, i + 1); -             if(P2.length () >longest.length ()) -Longest =P2; the         } -         returnlongest; -     } -  +      PublicString Expandfromcenter (String s,intC1,intC2) { -         intHead =C1; +         intTail =C2; A         intm =s.length (); at  -          while(Head >= 0 && tail < m && S.charat (head) = =S.charat (tail)) { -head--; -tail++; -         } -         returnS.substring (head + 1), tail); in     } -}

Java [Leetcode 5] Longest palindromic Substring