3370. Smallest Number With All Set Bits

You are given a positive number n.

Return the smallest number x greater than or equal to n, such that the binary representation of x contains only set bits.

A set bit refers to a bit in the binary representation of a number that has a value of 1.

class Solution {
public:
    int smallestNumber(int n) {
        int res = 1;
        while(res <= n) res *= 2;
        return res - 1;
    }
};