调用反向迭代器函数，rbegin，rend，判断回文串
class Solution {
public:
bool isPalindrome(string s) {
string sgood;
for (char ch: s) {
if (isalnum(ch)) {
sgood += tolower(ch);
}
}
string sgood_rev(sgood.rbegin(), sgood.rend());
return sgood == sgood_rev;
}
};
原文：https://www.cnblogs.com/zhangdalao/p/14610038.html