最长回文子串 C++

最长回文子串是指一个字符串中最长的回文子串，即正着读和倒着读都一样的子串。下面是 C++ 的实现代码：

#include <iostream>
#include <string>
using namespace std;

string longestPalindrome(string s) {
    int n = s.size();
    if (n < 2) return s;
    int start = 0, maxLen = 1;
    for (int i = 0; i < n; ) {
        if (n - i <= maxLen / 2) break;
        int j = i, k = i;
        while (k < n - 1 && s[k + 1] == s[k]) ++k;
        i = k + 1;
        while (k < n - 1 && j > 0 && s[k + 1] == s[j - 1]) {
            ++k;
            --j;
        }
        int newLen = k - j + 1;
        if (newLen > maxLen) {
            start = j;
            maxLen = newLen;
        }
    }
    return s.substr(start, maxLen);
}

int main() {
    string s = "babad";
    cout << longestPalindrome(s) << endl; // "bab" or "aba"
    return 0;
}