# 855. Exam Room 考场就座

## # 题目描述：

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. 1 <= N <= 10^9
2. ExamRoom.seat() and ExamRoom.leave() will be called at most 10^4 times across all test cases.
3. Calls to ExamRoom.leave(p) are guaranteed to have a student currently sitting in seat number p.

## # 解题方法

``````class ExamRoom(object):

def __init__(self, N):
"""
:type N: int
"""
self.N, self.L = N, list()

def seat(self):
"""
:rtype: int
"""
N, L = self.N, self.L
if not self.L: res = 0
else:
d, res = L[0], 0
# d means cur distance, res means cur pos
for a, b in zip(L, L[1:]):
if (b - a) / 2 > d:
d = (b - a) / 2
res = (b + a) / 2
if N - 1 - L[-1] > d:
res = N - 1
bisect.insort(L, res)
return res

def leave(self, p):
"""
:type p: int
:rtype: void
"""
self.L.remove(p)

# Your ExamRoom object will be instantiated and called as such:
# obj = ExamRoom(N)
# param_1 = obj.seat()
# obj.leave(p)
``````

https://leetcode.com/problems/exam-room/discuss/139862/C++JavaPython-Straight-Forward

## # 日期

2018 年 10 月 18 日 —— 做梦都在科研