题目地址：https://leetcode.com/problems/my-calendar-iii/description/
题目描述：
Implement a MyCalendarThree class to store your events. A new event can always be added.
Your class will have one method, book(int start, int end). Formally, this represents a booking on the half open interval [start, end), the range of real numbers x such that start <= x < end.
AK-booking happens when K events have some non-empty intersection (ie., there is some time that is common to all K events.)
Foreach call to the method MyCalendar.book, return an integer K representing the largest integer such that there exists a K-booking in the calendar.
Your class will be called like this: MyCalendarThree cal = new MyCalendarThree(); MyCalendarThree.book(start, end)
Example 1:
MyCalendarThree();
MyCalendarThree.book(10, 20); // returns 1
MyCalendarThree.book(50, 60); // returns 1
MyCalendarThree.book(10, 40); // returns 2
MyCalendarThree.book(5, 15); // returns 3
MyCalendarThree.book(5, 10); // returns 3
MyCalendarThree.book(25, 55); // returns 3
Explanation:
The first two events can be booked and are disjoint, so the maximum K-booking is a 1-booking.
The third event [10, 40) intersects the first event, and the maximum K-booking is a 2-booking.
The remaining events cause the maximum K-booking to be only a 3-booking.
Note that the last event locally causes a 2-booking, but the answer is still 3 because
eg. [10, 20), [10, 40), and [5, 15) are still triple booked.
Note:
1、 ThenumberofcallstoMyCalendarThree.bookpertestcasewillbeatmost400.；
2、 IncallstoMyCalendarThree.book(start,end),startandendareintegersintherange[0,10^9].；
解题方法
看这个：https://www.cnblogs.com/FannyChung/p/7896415.html
代码：
class Node(object):
def __init__(self, start, end, c):
self.start = start
self.end = end
self.count = c
self.left = None
self.right = None
class MyCalendarThree(object):
def __init__(self):
self.root = None
self.maxK = 1
def book_helper(self, root, start, end, c):
if root == None:
return Node(start, end, c)
if start >= root.end:
不能写成return self.boook_helper()，因为要进行树的构建和修改，一定要赋值给root.right
root.right = self.book_helper(root.right, start, end, c)
elif end <= root.start:
root.left = self.book_helper(root.left, start, end, c)
else:
intervals = sorted([start, end, root.start, root.end])
root_l, root_r = root.start, root.end
root.start, root.end = intervals[1], intervals[2]
root.left = self.book_helper(root.left, intervals[0], intervals[1], c if start <= root_l else root.count)
root.right = self.book_helper(root.right, intervals[2], intervals[3], c if end >= root_r else root.count)
root.count += c
self.maxK = max(root.count, self.maxK)
return root
def book(self, start, end):
"""
:type start: int
:type end: int
:rtype: int
"""
self.root = self.book_helper(self.root, start, end, 1)
return self.maxK
# Your MyCalendarThree object will be instantiated and called as such:
# obj = MyCalendarThree()
# param_1 = obj.book(start,end)
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