public:
    /**
     * 代码中的类名、方法名、参数名已经指定,请勿修改,直接返回方法规定的值即可
     *
     * 
     * @param A string字符串 
     * @return int整型
     */
    int getLongestPalindrome(string A) {
        if (A.size() < 2)
            return A.size();
        int maxlen = 0;
        for (int i=0; i<A.size()-1; i++){
            help(A, i, i, maxlen);
            help(A, i, i+1, maxlen);
        }
        return maxlen;
        // write code here
    }
    void help(string A, int left, int right, int& maxlen){
        while(left>=0 && right<A.size() && A[left]==A[right]){
            left--;
            right++;
        }
        if (maxlen < right - left - 1){
            maxlen = right - left - 1;
        }
    }
};
```https://www.cnblogs.com/grandyang/p/4464476.html