Leetcode#253. Meeting Rooms II

Given an array of meeting time intervals intervals where intervals[i] = [starti, endi], return the minimum number of conference rooms required.

Example 1:

Input: intervals = [[0,30],[5,10],[15,20]]
Output: 2

Example 2:

Input: intervals = [[7,10],[2,4]]
Output: 1

Constraints:

• 1 <= intervals.length <= 104
• 0 <= starti < endi <= 106

class Solution:
    def minMeetingRooms(self, intervals: List[List[int]]) -> int:
       # If there are no meetings, we don't need any rooms.
        if not intervals:
            return 0
num_rooms = 0
# Separate out the start and the end timings and sort them individually.
        start_timings = sorted(i[0] for i in intervals)
        end_timings = sorted(i[1] for i in intervals)
        L = len(intervals)
# The two pointers in the algorithm: e_ptr and s_ptr.
        end_pointer = 0
        start_pointer = 0
# Until all the meetings have been processed
        while start_pointer < L:
            # If there is a meeting that has ended by the time the meeting at `start_pointer` starts
            print(start_timings[start_pointer],end_timings[end_pointer])
            if start_timings[start_pointer] < end_timings[end_pointer]:
                # Free up a room and increment the end_pointer.
                num_rooms += 1
            else:
                end_pointer += 1
start_pointer += 1
return num_rooms