LeetCode 1903. Largest Odd Number in String

class Solution {
public:
    string largestOddNumber(string num) {
        const int n = num.size();
        int i = n - 1;
        for(; i >= 0; --i) {
            // if ((num[i] - '0') & 1) break;
             if (num[i] & 1) break; // ASCII code of an odd/even is also an odd/even.
        }
        return num.substr(0, i + 1);
    }
};