题解 | #密码截取#

#include <iostream>
#include <string>

using std::cout;
using std::endl;
using std::cin;
using std::string;

void test() {
    string str;
    cin >> str;
    int max_length = 0;
    int max_start = 0;
    int max_end = 0;
    int n = str.size();

    for (int i = 0; i < n; i++) {
        // 找到以当前字符为中心的奇数长度回文
        int left = i, right = i;
        while (left >= 0 && right < n && str[left] == str[right]) {
            if ((right - left + 1) > max_length) {
                max_length = right - left + 1;
                max_start = left;
                max_end = right;
            }
            left--;
            right++;
        }

        // 找到以当前字符和下一个字符为中心的偶数长度回文
        left = i;
        right = i + 1;
        while (left >= 0 && right < n && str[left] == str[right]) {
            if ((right - left + 1) > max_length) {
                max_length = right - left + 1;
                max_start = left;
                max_end = right;
            }
            left--;
            right++;
        }
    }

    cout << max_length << endl;
    // cout << "max_start = " << max_start << endl;
    // cout << "max_end = " << max_end << endl;
    // cout << str.substr(max_start, max_length) << endl;
}

int main(int argc, char* argv[]) {
    test();
    return 0;
}