[C++知识库]最长回文子串(C++)

#include <iostream>

using namespace std;

bool validStr(string s,int left,int right)
{
    while (left < right) {
        if(s.at(left) != s.at(right))
            return false;
        left++;
        right--;
    }
    return true;
}

string longestPalindrome(string s) {
    int len = s.length();
    int maxLen = 1;

    if(len < 2 )
    {
        cout << s;
        return s;
    }
    string res = s.substr(0,1);
    for (int i = 0; i < len - 1 ; i++) {
        for (int j = i + 1; j < len; j++) {
            if (j - i + 1 > maxLen && validStr(s, i, j)) {
                maxLen = j - i + 1;
                res = s.substr(i,maxLen);
            }
        }
    }
    cout << res;
    return res;
}


int main()
{
    longestPalindrome("abc");
//    longestPalindrome("a");
//    longestPalindrome("abab");
//    longestPalindrome("abab78987");
//    longestPalindrome("aa678");
    return 0;
}