3169. Count Days Without Meetings

You are given a positive integer days representing the total number of days an employee is available for work (starting from day 1). You are also given a 2D array meetings of size n where, meetings[i] = [start_i, end_i] represents the starting and ending days of meeting i (inclusive).

Return the count of days when the employee is available for work but no meetings are scheduled.

Note: The meetings may overlap.

class Solution {
public:
    int countDays(int days, vector<vector<int>>& A) {
        sort(rbegin(A), rend(A));
        while(A.size()) {
            int s = A.back()[0], e = A.back()[1];
            while(A.size() and A.back()[0] <= e + 1) {
                e = max(e, A.back()[1]);
                A.pop_back();
            }
            days -= (e - s + 1);
        }
        return days;
    }
};