Longest Palindromic Substring 題解

原創文章，拒絕轉載

題目來源：https://leetcode.com/problems/longest-palindromic-substring/description/

Description

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.
 

Input: "cbbd"

Output: "bb"

Solution

class Solution {
private:
    int resStart;
    int resSize;
    int inSize;
    void expandPalindrome(string& s, int start, int end) {
        while (start >= 0 && end < inSize && s[start] == s[end]) {
            start--;
            end++;
        }
        start++;
        int
 
 temp = end - start;
        if (temp > resSize) {
            resSize = temp;
            resStart = start;
        }
    }
public:
    string longestPalindrome(string s) {
        inSize = s.length();
        if (inSize <= 1)
            return s;
        resStart = resSize = 0;
        for (int
 
 i = 0; i < inSize - 1; i++) {
            expandPalindrome(s, i, i); // 求奇數長度的回文子串
            expandPalindrome(s, i, i + 1); // 求偶數長度的回文子串
        }
        return s.substr(resStart, resSize);
    }
};

解題描述

這道題考察的是求一個字符串中的最長回文子串。而對每一個非空的輸入串來說，其回文子串最短為1，因此可以對字符串中的每一個元素，同時向左和向右探測，直到回文子串結束，每次判斷得到的子串是否是最長的即可。

[Leetcode]Longest Palindromic Substring