[LeetCode] Meeting Rooms I & II

Meeting Rooms

Given an array of meeting time intervals consisting of start and end times [[s1,e1],[s2,e2],...] (si < ei), determine if a person could attend all meetings.

For example,
Given [[0, 30],[5, 10],[15, 20]],
return false.

/**
 * Definition for an interval.
 * struct Interval {
 *     int start;
 *     int end;
 *     Interval() : start(0), end(0) {}
 *     Interval(int s, int e) : start(s), end(e) {}
 * };
 */
class Solution {
public:
    bool canAttendMeetings(vector<Interval>& intervals) {
        sort(intervals.begin(), intervals.end(), [](const Interval &a, const Interval &b) {
            return a.start < b.start;
        });
        for (int i = 1; i < intervals.size(); ++i) {
            if (intervals[i].start < intervals[i-1].end) return false;
        }
        return true;
    }
};

Meeting Rooms II

Given an array of meeting time intervals consisting of start and end times [[s1,e1],[s2,e2],...] (si < ei), find the minimum number of conference rooms required.

For example,
Given [[0, 30],[5, 10],[15, 20]],
return 2.

/**
 * Definition for an interval.
 * struct Interval {
 *     int start;
 *     int end;
 *     Interval() : start(0), end(0) {}
 *     Interval(int s, int e) : start(s), end(e) {}
 * };
 */
class Solution {
public:
    int minMeetingRooms(vector<Interval>& intervals) {
        vector<pair<int, int>> schedule;
        for (auto interval : intervals) {
            schedule.push_back({interval.start, 1});
            schedule.push_back({interval.end, -1});
        }
        sort(schedule.begin(), schedule.end());
        int cnt = 0, res = 0;
        for (auto s : schedule) {
            if (s.second == 1) ++cnt;
            else --cnt;
            res = max(res, cnt);
        }
        return res;
    }
};