2549. Count Distinct Numbers on Board

You are given a positive integer n, that is initially placed on a board. Every day, for 109 days, you perform the following procedure:

• For each number x present on the board, find all numbers 1 <= i <= n such that x % i == 1.
• Then, place those numbers on the board.

Return the number of distinct integers present on the board after 109 days have elapsed.

Note:

• Once a number is placed on the board, it will remain on it until the end.
• % stands for the modulo operation. For example, 14 % 3 is 2.

class Solution {
public:
    int distinctIntegers(int n) {
        int res = 1;
        unordered_set<int> us{n};
        queue<int> q;
        q.push(n);
        while(!q.empty()) {
            int u = q.front(); q.pop();
            for(int i = 1; i < u; i++) {
                if(u % i == 1 and !us.count(i)) {
                    res += 1;
                    us.insert(i);
                    q.push(i);
                }
            }
        }
        return res;
    }
};