Leetcode: Palindrome Number

class Solution {
public:
    bool isPalindrome(int x) { // 123
        if (x < 0) return false;
        
        long long num = x;

        // find the high digit
        int h = 11;
        while (h >= 0 && digit(h, num) == 0) h--;

        // matching
        int l = 0;
        while (l < h) {
            if (digit(h, num) != digit(l, num)) return false;
            l++; h--;
        }
        return true;
    }
    // idx starting from 0
    long long digit(int idx, long long num) {
        long long base = (long long) pow(10, idx);
        long long cut = (long long) pow(10, idx+1);
        return (num%cut) / base;
    }
};