Formatted question description: https://leetcode.ca/all/732.html

732. My Calendar III

Level

Hard

Description

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.

A K-booking happens when K events have some non-empty intersection (ie., there is some time that is common to all K events.)

For each 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:

The number of calls to MyCalendarThree.book per test case will be at most 400.
In calls to MyCalendarThree.book(start, end), start and end are integers in the range [0, 10^9].

Solution

Use TreeMap, which contains all keys in sorted order. Each time book(int start, int end) is called, update the values of the keys start and end in the map by increasing the value of key start by 1 and decreasing the value of key end by 1. Then loop over all the keys in the map to obtain the booking count of each time and the maximum booking, and return the maximum booking.

import java.util.TreeMap;

public class My_Calendar_III {

    // ref: https://leetcode.com/articles/my-calendar-iii/

    // `start+1` and `end-1`
    class MyCalendarThree {

        TreeMap<Integer, Integer> timeCountMap;

        public MyCalendarThree() {
            timeCountMap = new TreeMap<>();
        }

        public int book(int start, int end) {

            timeCountMap.put(start, timeCountMap.getOrDefault(start, 0) + 1);
            timeCountMap.put(end, timeCountMap.getOrDefault(end, 0) - 1);

            int active = 0;
            int result = 0;

            for (int d : timeCountMap.values()) {
                active += d;
                result = Math.max(result, active);
            }

            return result;
        }
    }
}

// OJ: https://leetcode.com/problems/my-calendar-iii/
// Time:
//      MyCalendarThree: O(1)
//      book: O(N)
// Space: O(N)
class MyCalendarThree {
    map<int, int> m;
public:
    MyCalendarThree() {}
    int book(int start, int end) {
        m[start]++;
        m[end]--;
        int ans = 1, cur = 0;
        for (auto &[p, d] : m) {
            ans = max(ans, cur += d);
        }
        return ans;
    }
};

from sortedcontainers import SortedDict


class MyCalendarThree:
  def __init__(self):
    self.timeline = SortedDict()

  def book(self, start: int, end: int) -> int:
    self.timeline[start] = self.timeline.get(start, 0) + 1
    self.timeline[end] = self.timeline.get(end, 0) - 1

    ans = 0
    activeEvents = 0

    for count in self.timeline.values():
      activeEvents += count
      ans = max(ans, activeEvents)

    return ans

############

class Node:
    def __init__(self, l, r):
        self.left = None
        self.right = None
        self.l = l
        self.r = r
        self.mid = (l + r) >> 1
        self.v = 0
        self.add = 0


class SegmentTree: # <===
    def __init__(self):
        self.root = Node(1, int(1e9 + 1))

    def modify(self, l, r, v, node=None):
        if l > r:
            return
        if node is None:
            node = self.root
        if node.l >= l and node.r <= r:
            node.v += v
            node.add += v
            return
        self.pushdown(node)
        if l <= node.mid:
            self.modify(l, r, v, node.left)
        if r > node.mid:
            self.modify(l, r, v, node.right)
        self.pushup(node)

    def query(self, l, r, node=None):
        if l > r:
            return 0
        if node is None:
            node = self.root
        if node.l >= l and node.r <= r:
            return node.v
        self.pushdown(node)
        v = 0
        if l <= node.mid:
            v = max(v, self.query(l, r, node.left))
        if r > node.mid:
            v = max(v, self.query(l, r, node.right))
        return v

    def pushup(self, node):
        node.v = max(node.left.v, node.right.v)

    def pushdown(self, node):
        if node.left is None:
            node.left = Node(node.l, node.mid)
        if node.right is None:
            node.right = Node(node.mid + 1, node.r)
        if node.add:
            node.left.v += node.add
            node.right.v += node.add
            node.left.add += node.add
            node.right.add += node.add
            node.add = 0


class MyCalendarThree:
    def __init__(self):
        self.tree = SegmentTree()

    def book(self, start: int, end: int) -> int:
        self.tree.modify(start + 1, end, 1)
        return self.tree.query(1, int(1e9 + 1))


# Your MyCalendarThree object will be instantiated and called as such:
# obj = MyCalendarThree()
# param_1 = obj.book(start,end)

############

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)

732 - My Calendar III

732. My Calendar III

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732. My Calendar III

Level

Description

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All Problems

All Solutions