Algorithm
Problem Name: 855. Exam Room
Problem Link: https://leetcode.com/problems/exam-room/
There is an exam room with n seats in a single row labeled from 0 to 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. If no one is in the room, then the student sits at seat number 0.
Design a class that simulates the mentioned exam room.
Implement the ExamRoom class:
ExamRoom(int n)Initializes the object of the exam room with the number of the seatsn.int seat()Returns the label of the seat at which the next student will set.void leave(int p)Indicates that the student sitting at seatpwill leave the room. It is guaranteed that there will be a student sitting at seatp.
Example 1:
Input ["ExamRoom", "seat", "seat", "seat", "seat", "leave", "seat"] [[10], [], [], [], [], [4], []] Output [null, 0, 9, 4, 2, null, 5] Explanation ExamRoom examRoom = new ExamRoom(10); examRoom.seat(); // return 0, no one is in the room, then the student sits at seat number 0. examRoom.seat(); // return 9, the student sits at the last seat number 9. examRoom.seat(); // return 4, the student sits at the last seat number 4. examRoom.seat(); // return 2, the student sits at the last seat number 2. examRoom.leave(4); examRoom.seat(); // return 5, the student sits at the last seat number 5.
Constraints:
1 <= n <= 109- It is guaranteed that there is a student sitting at seat
p. - At most
104calls will be made toseatandleave.
Code Examples
#1 Code Example with C++ Programming
Code -
C++ Programming
class ExamRoom {
public:
ExamRoom(int N) {
this->N = N;
}
int seat() {
if (s.size() == 0) {
s.insert(0);
return 0;
} else if (s.size() == 1) {
int pos = *s.begin() < N/2 ? N - 1 : 0;
s.insert(pos);
return pos;
} else {
int maxDis = -1;
int res = -1;
if (!s.count(0)) {
maxDis = *s.begin() - 1;
res = 0;
}
auto p1 = s.begin();
auto p2 = p1;
++p2;
while (p2 != s.end()) {
int pos = (*p2 + *p1)/2;
int d = min(pos - *p1, *p2 - pos) - 1;
if (d > maxDis) {
maxDis = d;
res = (*p1 + *p2)/2;
}
++p1;
++p2;
}
if (!s.count(N - 1)) {
auto e = s.end();
--e;
int d = N - 1 - *e - 1;
if (d > maxDis) {
res = N - 1;
}
}
s.insert(res);
return res;
}
}
void leave(int p) {
s.erase(p);
}
private:
set < int>s;
int N;
};
Input
["ExamRoom", "seat", "seat", "seat", "seat", "leave", "seat"]
[[10], [], [], [], [], [4], []]
Output
[null, 0, 9, 4, 2, null, 5]
#2 Code Example with Javascript Programming
Code -
Javascript Programming
const ExamRoom = function(n) {
let a = [];
return { seat, leave }
function seat() {
if (a.length == 0) {
a.push(0);
return 0;
}
let dis = Math.max(a[0], n - 1 - a[a.length - 1]);
for (let i = 1; i < a.length; i++) dis = Math.max(dis, a[i] - a[i - 1] >> 1);
if (a[0] == dis) {
a.unshift(0);
return 0;
}
for (let i = 1; i < a.length; i++) {
if (a[i] - a[i - 1] >> 1 == dis) {
a.splice(i, 0, a[i] + a[i - 1] >> 1);
return a[i];
}
}
a.push(n - 1);
return n - 1;
}
function leave(p) {
for (let i = 0; i < a.length; i++) {
if (a[i] == p) {
a.splice(i, 1);
break;
}
}
}
};
Input
["ExamRoom", "seat", "seat", "seat", "seat", "leave", "seat"]
[[10], [], [], [], [], [4], []]
Output
[null, 0, 9, 4, 2, null, 5]
#3 Code Example with Python Programming
Code -
Python Programming
class ExamRoom:
def __init__(self, N):
self.seated, self.n = [], N - 1
def seat(self):
if not self.seated:
self.seated += 0,
return 0
mx = ind = 0
for i in range(1, len(self.seated)):
l, r = self.seated[i - 1], self.seated[i]
if (r - l) // 2 > mx:
mx = (r - l) // 2
ind = l + mx
if self.seated[-1] != self.n and self.n - self.seated[-1] > mx:
mx, ind = self.n - self.seated[-1], self.n
if self.seated[0] >= mx:
mx, ind = self.seated[0], 0
self.seated.append(ind)
self.seated.sort()
return ind
def leave(self, p):
self.seated.remove(p)
Input
["ExamRoom", "seat", "seat", "seat", "seat", "leave", "seat"]
[[10], [], [], [], [], [4], []]
Output
[null, 0, 9, 4, 2, null, 5]