class Solution {
public:
    string longestPalindrome(string s) {
        if (s.size() <= 1){
            return s;
        }

        int a = 0;  //记录临时值
        int length = 0;

        int ta = 1; //滑动窗口边界
        int tb = 0;

        int t = 0;

        bool flag = false;  //匹配标记

        const char* p = s.c_str();
        for(int i=0;i<s.size();i++){            
            for(int j = i + length;j<s.size();j++){
                t = (j-i+1);                
                tb = t/2;

                for(int k =i;k<(i+tb);k++){
                    if (p[k] != p[j - k + i]) {
                        flag = true;
                        break;
                    }
                }
                
                if (!flag){
                    if (t > length){
                        a = i;
                        length = t;
                    }
                }
                flag = false;
            }
        }

        if (a == 0 && length == 0) {
            length = 1;
        }
        return s.substr(a,length);
    }
};