[Swift]LeetCode855. 考场就座 | Exam Room
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In an exam room, there are N seats in a single row, numbered 0, 1, 2, ..., N-1.
When a student enters the room, they must sit in the seat that maximizes the distance to the closest person. If there are multiple such seats, they sit in the seat with the lowest number. (Also, if no one is in the room, then the student sits at seat number 0.)
Return a class ExamRoom(int N) that exposes two functions: ExamRoom.seat() returning an int representing what seat the student sat in, and ExamRoom.leave(int p) representing that the student in seat number p now leaves the room. It is guaranteed that any calls to ExamRoom.leave(p) have a student sitting in seat p.
Example 1:
Input: ["ExamRoom","seat","seat","seat","seat","leave","seat"], [[10],[],[],[],[],[4],[]]
Output: [null,0,9,4,2,null,5]
Explanation:
ExamRoom(10) -> null
seat() -> 0, no one is in the room, then the student sits at seat number 0.
seat() -> 9, the student sits at the last seat number 9.
seat() -> 4, the student sits at the last seat number 4.
seat() -> 2, the student sits at the last seat number 2.
leave(4) -> null
seat() -> 5, the student sits at the last seat number 5.
Note:
1 <= N <= 10^9ExamRoom.seat()andExamRoom.leave()will be called at most10^4times across all test cases.- Calls to
ExamRoom.leave(p)are guaranteed to have a student currently sitting in seat numberp.
在考场里，一排有 N 个座位，分别编号为 0, 1, 2, ..., N-1 。
当学生进入考场后，他必须坐在能够使他与离他最近的人之间的距离达到最大化的座位上。如果有多个这样的座位，他会坐在编号最小的座位上。(另外，如果考场里没有人，那么学生就坐在 0 号座位上。)
返回 ExamRoom(int N) 类，它有两个公开的函数：其中，函数 ExamRoom.seat() 会返回一个 int （整型数据），代表学生坐的位置；函数 ExamRoom.leave(int p) 代表坐在座位 p上的学生现在离开了考场。请确保每次调用 ExamRoom.leave(p) 时都有学生坐在座位 p 上。
示例：
输入：["ExamRoom","seat","seat","seat","seat","leave","seat"], [[10],[],[],[],[],[4],[]] 输出：[null,0,9,4,2,null,5] 解释： ExamRoom(10) -> null seat() -> 0，没有人在考场里，那么学生坐在 0 号座位上。 seat() -> 9，学生最后坐在 9 号座位上。 seat() -> 4，学生最后坐在 4 号座位上。 seat() -> 2，学生最后坐在 2 号座位上。 leave(4) -> null seat() -> 5，学生最后坐在 5 号座位上。
提示：
1 <= N <= 10^9- 在所有的测试样例中
ExamRoom.seat()和ExamRoom.leave()最多被调用10^4次。 - 调用
ExamRoom.leave(p)时需要确保当前有学生坐在座位p上。
336ms
1 class ExamRoom { 2 var students: [Int] 3 let N: Int 4 5 init(_ N: Int) { 6 students = [Int]() 7 self.N = N 8 } 9 10 // with sort it's O(PlogP), with index it's O(P) 11 func seat() -> Int { 12 var student = 0 13 var index = 0 14 if students.count > 0 { 15 var prev: Int? = nil 16 var dist = students.first ?? 0 17 for (i, studentPos) in students.enumerated() { 18 if let prev = prev { 19 let d: Int = (studentPos - prev) / 2 20 if d > dist { 21 dist = d 22 student = prev + d 23 index = i 24 } 25 } 26 prev = studentPos 27 } 28 if N - 1 - (students.last ?? 0) > dist { 29 student = N - 1 30 index = students.count 31 } 32 } 33 students.insert(student, at: index) 34 return student 35 } 36 37 // O(P), because of remove. 38 func leave(_ p: Int) { 39 for i in 0..<students.count { 40 if students[i] == p { 41 students.remove(at: i) 42 return 43 } 44 } 45 } 46 } 47 48 // wrong 49 class ExamRoom1 { 50 51 var seats: [Bool] 52 53 init(_ N: Int) { 54 seats = Array(repeating: false, count: N) 55 } 56 57 func seat() -> Int { 58 let index = findSeat(0, seats.count - 1) 59 seats[index] = true 60 return index 61 } 62 63 func leave(_ p: Int) { 64 seats[p] = false 65 } 66 67 private func findSeat(_ l: Int, _ r: Int) -> Int { 68 if seats[l] == false { 69 return 0 70 } 71 if seats[r] == false { 72 return r 73 } 74 let m = (l + r) / 2 75 if seats[m] == false { 76 return m 77 } 78 let lh = findSeat(l, m) 79 if seats[lh] == false { 80 return lh 81 } 82 83 let rh = findSeat(m, r) 84 if seats[rh] == false { 85 return rh 86 } 87 return -1 88 } 89 } 90 91 /** 92 * Your ExamRoom object will be instantiated and called as such: 93 * let obj = ExamRoom(N) 94 * let ret_1: Int = obj.seat() 95 * obj.leave(p) 96 */
1 class ExamRoom { 2 static var N:Int = 0 3 var pq:[Interval] = [Interval]() 4 5 init(_ N: Int) { 6 ExamRoom.N = N 7 pq.append(Interval(-1, N)) 8 } 9 10 func seat() -> Int { 11 var seat:Int = 0 12 var interval:Interval = pq.removeFirst() 13 if interval.x == -1 {seat = 0} 14 else if interval.y == ExamRoom.N {seat = ExamRoom.N - 1} 15 else {seat = (interval.x + interval.y) / 2} 16 offer(Interval(interval.x, seat)) 17 offer(Interval(seat, interval.y)) 18 return seat 19 } 20 21 func leave(_ p: Int) { 22 var head:Interval? = nil 23 var tail:Interval? = nil 24 for interval in pq 25 { 26 if interval.x == p {tail = interval} 27 if interval.y == p {head = interval} 28 if head != nil && tail != nil {break} 29 } 30 removeEle(head!) 31 removeEle(tail!) 32 offer(Interval(head!.x, tail!.y)) 33 } 34 35 func removeEle(_ interval:Interval) 36 { 37 for i in (0..<pq.count).reversed() 38 { 39 if pq[i].x == interval.x && pq[i].y == interval.y && pq[i].dist == interval.dist 40 { 41 pq.remove(at:i) 42 } 43 } 44 } 45 46 func offer(_ interval:Interval) 47 { 48 pq.append(interval) 49 pq.sort(by:{(a:Interval,b:Interval) -> Bool in 50 if a.dist == b.dist 51 { 52 return a.x <= b.x 53 } 54 else 55 { 56 return a.dist > b.dist 57 } 58 }) 59 } 60 } 61 62 class Interval{ 63 var x:Int 64 var y:Int 65 var dist:Int 66 init(_ x:Int,_ y:Int) 67 { 68 self.x = x 69 self.y = y 70 if x == -1 71 { 72 self.dist = y 73 } 74 else if y == ExamRoom.N 75 { 76 self.dist = ExamRoom.N - 1 - x 77 } 78 else 79 { 80 self.dist = abs(x - y) / 2 81 } 82 } 83 } 84 85 /** 86 * Your ExamRoom object will be instantiated and called as such: 87 * let obj = ExamRoom(N) 88 * let ret_1: Int = obj.seat() 89 * obj.leave(p) 90 */
