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5 | 5 |
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6 | 6 | public class _253 { |
7 | 7 | public static class Solution1 { |
8 | | - |
9 | 8 | public int minMeetingRooms(int[][] intervals) { |
10 | 9 | if (intervals == null || intervals.length == 0) { |
11 | 10 | return 0; |
12 | 11 | } |
13 | | - |
14 | | - // Sort the intervals by start time |
15 | | - Arrays.sort(intervals, (a, b) -> a[0] - b[0]); |
16 | | - |
17 | | - // Use a min heap to track the minimum end time of merged intervals |
18 | | - PriorityQueue<int[]> heap = new PriorityQueue<>(intervals.length, (a, b) -> a[1] - b[1]); |
19 | | - |
20 | | - // start with the first meeting, put it to a meeting room |
21 | | - heap.offer(intervals[0]); |
22 | | - |
| 12 | + Arrays.sort(intervals, (a, b) -> a[0] - b[0]);// Sort the intervals by start time |
| 13 | + PriorityQueue<int[]> heap = new PriorityQueue<>(intervals.length, (a, b) -> a[1] - b[1]);// Use a min heap to track the minimum end time of merged intervals |
| 14 | + heap.offer(intervals[0]);// start with the first meeting, put it to a meeting room |
23 | 15 | for (int i = 1; i < intervals.length; i++) { |
24 | 16 | // get the meeting room that finishes earliest |
25 | | - int[] interval = heap.poll(); |
26 | | - |
27 | | - if (intervals[i][0] >= interval[1]) { |
| 17 | + int[] last = heap.poll(); |
| 18 | + if (intervals[i][0] >= last[1]) { |
28 | 19 | // if the current meeting starts right after |
29 | 20 | // there's no need for a new room, merge the interval |
30 | | - interval[1] = intervals[i][1]; |
| 21 | + last[1] = intervals[i][1]; |
31 | 22 | } else { |
32 | 23 | // otherwise, this meeting needs a new room |
33 | 24 | heap.offer(intervals[i]); |
34 | 25 | } |
35 | | - |
36 | 26 | // don't forget to put the meeting room back |
37 | | - heap.offer(interval); |
| 27 | + heap.offer(last); |
38 | 28 | } |
39 | 29 |
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40 | 30 | return heap.size(); |
41 | 31 | } |
42 | 32 | } |
43 | | - |
44 | | - public static class Solution2 { |
45 | | - /** |
46 | | - * I'm so glad to have come up with this solution completely on my own on 10/13/2021. |
47 | | - * Drawing on a piece of paper helps A LOT! It helps visualize your thoughts and clear the ambiguity up! |
48 | | - */ |
49 | | - public int minMeetingRooms(int[][] intervals) { |
50 | | - //I use the meeting's end time as the room indicate and put them into a heap |
51 | | - PriorityQueue<Integer> rooms = new PriorityQueue<>(); |
52 | | - Arrays.sort(intervals, (a, b) -> a[0] - b[0]); |
53 | | - for (int i = 0; i < intervals.length; i++) { |
54 | | - if (rooms.isEmpty()) { |
55 | | - rooms.add(intervals[i][1]); |
56 | | - } else { |
57 | | - if (rooms.peek() > intervals[i][0]) { |
58 | | - //if the room that becomes available the earliest still cannot accommodate this new meeting, then we'll have to add a new room |
59 | | - rooms.add(intervals[i][1]); |
60 | | - } else { |
61 | | - //otherwise, we'll just update the room that finishes the earliest with the new finish time. |
62 | | - rooms.poll(); |
63 | | - rooms.add(intervals[i][1]); |
64 | | - } |
65 | | - } |
66 | | - } |
67 | | - return rooms.size(); |
68 | | - } |
69 | | - } |
70 | 33 | } |
71 | 34 |
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