number-of-students-doing-homework-at-a-given-time.cpp

// Time:  O(n)
// Space: O(1)

class Solution {
public:
    int busyStudent(vector<int>& startTime, vector<int>& endTime, int queryTime) {
        int result = 0;
        for (int i = 0; i < startTime.size(); ++i) {
            if (startTime[i] <= queryTime && queryTime <= endTime[i]) {
                ++result;
            }
        }
        return result;
    }
};