New Problem Solution - "1845. Seat Reservation Manager"

README.md

@@ -9,6 +9,7 @@ LeetCode
 
 | # | Title | Solution | Difficulty |
 |---| ----- | -------- | ---------- |
+|1845|[Seat Reservation Manager](https://leetcode.com/problems/seat-reservation-manager/) | [C++](./algorithms/cpp/seatReservationManager/SeatReservationManager.cpp)|Medium|
 |1844|[Replace All Digits with Characters](https://leetcode.com/problems/replace-all-digits-with-characters/) | [C++](./algorithms/cpp/replaceAllDigitsWithCharacters/ReplaceAllDigitsWithCharacters.cpp)|Easy|
 |1840|[Maximum Building Height](https://leetcode.com/problems/maximum-building-height/) | [C++](./algorithms/cpp/maximumBuildingHeight/MaximumBuildingHeight.cpp)|Hard|
 |1839|[Longest Substring Of All Vowels in Order](https://leetcode.com/problems/longest-substring-of-all-vowels-in-order/) | [C++](./algorithms/cpp/longestSubstringOfAllVowelsInOrder/LongestSubstringOfAllVowelsInOrder.cpp)|Medium|

algorithms/cpp/seatReservationManager/SeatReservationManager.cpp

@@ -0,0 +1,78 @@
+// Source : https://leetcode.com/problems/seat-reservation-manager/
+// Author : Hao Chen
+// Date   : 2021-05-03
+
+/***************************************************************************************************** 
+ *
+ * Design a system that manages the reservation state of n seats that are numbered from 1 to n.
+ * 
+ * Implement the SeatManager class:
+ * 
+ * 	SeatManager(int n) Initializes a SeatManager object that will manage n seats numbered from 
+ * 1 to n. All seats are initially available.
+ * 	int reserve() Fetches the smallest-numbered unreserved seat, reserves it, and returns its 
+ * number.
+ * 	void unreserve(int seatNumber) Unreserves the seat with the given seatNumber.
+ * 
+ * Example 1:
+ * 
+ * Input
+ * ["SeatManager", "reserve", "reserve", "unreserve", "reserve", "reserve", "reserve", "reserve", 
+ * "unreserve"]
+ * [[5], [], [], [2], [], [], [], [], [5]]
+ * Output
+ * [null, 1, 2, null, 2, 3, 4, 5, null]
+ * 
+ * Explanation
+ * SeatManager seatManager = new SeatManager(5); // Initializes a SeatManager with 5 seats.
+ * seatManager.reserve();    // All seats are available, so return the lowest numbered seat, which is 
+ * 1.
+ * seatManager.reserve();    // The available seats are [2,3,4,5], so return the lowest of them, which 
+ * is 2.
+ * seatManager.unreserve(2); // Unreserve seat 2, so now the available seats are [2,3,4,5].
+ * seatManager.reserve();    // The available seats are [2,3,4,5], so return the lowest of them, which 
+ * is 2.
+ * seatManager.reserve();    // The available seats are [3,4,5], so return the lowest of them, which 
+ * is 3.
+ * seatManager.reserve();    // The available seats are [4,5], so return the lowest of them, which is 
+ * 4.
+ * seatManager.reserve();    // The only available seat is seat 5, so return 5.
+ * seatManager.unreserve(5); // Unreserve seat 5, so now the available seats are [5].
+ * 
+ * Constraints:
+ * 
+ * 	1 <= n <= 10^5
+ * 	1 <= seatNumber <= n
+ * 	For each call to reserve, it is guaranteed that there will be at least one unreserved seat.
+ * 	For each call to unreserve, it is guaranteed that seatNumber will be reserved.
+ * 	At most 10^5 calls in total will be made to reserve and unreserve.
+ ******************************************************************************************************/
+
+class SeatManager {
+private:
+    set<int> idle;
+public:
+    SeatManager(int n) {
+        for(int i=1; i<=n; i++) {
+            idle.insert(i);
+        }
+    }
+    
+    int reserve() {
+        auto it = idle.begin();
+        auto seat = *it;
+        idle.erase(it);
+        return seat;
+    }
+    
+    void unreserve(int seatNumber) {
+        idle.insert(seatNumber);
+    }
+};
+
+/**
+ * Your SeatManager object will be instantiated and called as such:
+ * SeatManager* obj = new SeatManager(n);
+ * int param_1 = obj->reserve();
+ * obj->unreserve(seatNumber);
+ */