Add 'Meeting Rooms II'

Author: nickolashkraus

README.md

@@ -64,6 +64,8 @@ A collection of LeetCode solutions
 
 [Meeting Rooms](./src/meeting_rooms.py)
 
+[Meeting Rooms II](./src/meeting_rooms_ii.py)
+
 [Merge Intervals](./src/merge_intervals.py)
 
 [Merge k Sorted Lists](./src/merge_k_sorted_lists.py)

src/meeting_rooms_ii.py

@@ -0,0 +1,35 @@
+"""
+253. Meeting Rooms II
+
+https://leetcode.com/problems/meeting-rooms-ii
+
+NOTES
+  * Maintain a min-heap of meeting end times. The minimum (earliest) end time
+    is the root node (heap invariant). If the end time of the root node is less
+    than or equal to the start time of the current node, delete the root node
+    from the heap. Insert the meeting end time into the heap. This is roughly
+    equivalent to allocating/deallocating conference rooms for each meeting.
+    The minimum number of conference rooms required is then the maximum size of
+    the heap.
+
+I really love this one–mainly due to the elegant use of a heap and because I
+just love heaps <3.
+"""
+
+import heapq
+
+
+class Solution:
+    def minMeetingRooms(self, intervals: list[list[int]]) -> int:
+        intervals.sort(key=lambda x: x[0])
+        heap: list[int] = []
+        min_rooms = 0
+        for interval in intervals:
+            if len(heap) == 0:
+                heapq.heappush(heap, interval[1])
+            else:
+                if heap[0] <= interval[0]:
+                    heapq.heappop(heap)
+                heapq.heappush(heap, interval[1])
+            min_rooms = max(min_rooms, len(heap))
+        return min_rooms

tests/test_meeting_rooms_ii.py

@@ -0,0 +1,27 @@
+"""
+253. Meeting Rooms II
+
+https://leetcode.com/problems/meeting-rooms-ii
+"""
+
+from unittest import TestCase
+
+from src.meeting_rooms_ii import Solution
+
+
+class TestSolution(TestCase):
+    def test_1(self):
+        exp = 2
+        assert Solution().minMeetingRooms([[0, 30], [5, 10], [15, 20]]) == exp
+
+    def test_2(self):
+        exp = 1
+        assert Solution().minMeetingRooms([[7, 10], [2, 4]]) == exp
+
+    def test_3(self):
+        exp = 2
+        assert Solution().minMeetingRooms([[5, 8], [6, 8]]) == exp
+
+    def test_4(self):
+        exp = 2
+        assert Solution().minMeetingRooms([[9, 10], [4, 9], [4, 17]]) == exp