1903. Largest Odd Number in String

You are given a string num, representing a large integer. Return the largest-valued odd integer (as a string) that is a non-empty substring of num, or an empty string “” if no odd integer exists.

A substring is a contiguous sequence of characters within a string.

class Solution {
public:
    string largestOddNumber(string num) {
        while(num.length() && !((num.back() & 0b1111) % 2)) num.pop_back();
        return num;
    }
};