Create meeting-rooms-ii.cpp

C++/meeting-rooms-ii.cpp

@@ -0,0 +1,40 @@
+// Time:  O(nlogn)
+// Space: O(n)
+
+/**
+ * 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<int> starts, ends;
+        for (const auto& i : intervals) {
+            starts.emplace_back(i.start);
+            ends.emplace_back(i.end);
+        }
+
+        sort(starts.begin(), starts.end());
+        sort(ends.begin(), ends.end());
+
+        int min_rooms = 0, cnt_rooms = 0;
+        int s = 0, e = 0;
+        while (s < starts.size()) {
+            if (starts[s] < ends[e]) {
+                ++cnt_rooms;  // Acquire a room.
+                // Update the min number of rooms.
+                min_rooms = max(min_rooms, cnt_rooms);
+                ++s;
+            } else {
+                --cnt_rooms;  // Release a room.
+                ++e;
+            }
+        }
+        return min_rooms;
+    }
+};