leetcode 9 Palindrome Number

c++:

class Solution {
public:
    bool isPalindrome(int x) {
        if(x<0) return false;
        std::string str = std::to_string(x);
        for(std::string::iterator i = str.begin(), j = str.end()-1; i < j; i++, j--){
            if(*i != *j)
                return false;
        }
        return true;
    }
};