RUST GYM Leetcode 732 My Calendar III Rust Solution

732. My Calendar III

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

You are given some events [start, end), after each given event, return an integer k representing the maximum k-booking between all the previous events.

Implement the MyCalendarThree class:

MyCalendarThree() Initializes the object.
int book(int start, int end) Returns an integer k representing the largest integer such that there exists a k-booking in the calendar.

Example 1:

Input
["MyCalendarThree", "book", "book", "book", "book", "book", "book"]
[[], [10, 20], [50, 60], [10, 40], [5, 15], [5, 10], [25, 55]]
Output
[null, 1, 1, 2, 3, 3, 3]

Explanation
MyCalendarThree myCalendarThree = new MyCalendarThree();
myCalendarThree.book(10, 20); // return 1, The first event can be booked and is disjoint, so the maximum k-booking is a 1-booking.
myCalendarThree.book(50, 60); // return 1, The second event can be booked and is disjoint, so the maximum k-booking is a 1-booking.
myCalendarThree.book(10, 40); // return 2, The third event [10, 40) intersects the first event, and the maximum k-booking is a 2-booking.
myCalendarThree.book(5, 15); // return 3, The remaining events cause the maximum K-booking to be only a 3-booking.
myCalendarThree.book(5, 10); // return 3
myCalendarThree.book(25, 55); // return 3

Constraints:

0 <= start < end <= 10⁹
At most 400 calls will be made to book.

Rust Solution

use std::collections::BTreeMap;

struct MyCalendarThree {
    data: BTreeMap<i32, i32>,
}

impl MyCalendarThree {
    fn new() -> Self {
        let data = BTreeMap::new();
        MyCalendarThree { data }
    }

    fn book(&mut self, start: i32, end: i32) -> i32 {
        *self.data.entry(start).or_default() += 1;
        *self.data.entry(end).or_default() -= 1;
        let mut cur = 0;
        let mut res = 0;
        for v in self.data.values() {
            cur += v;
            res = res.max(cur);
        }
        res
    }
}

#[test]
fn test() {
    let mut obj = MyCalendarThree::new();
    assert_eq!(obj.book(10, 20), 1);
    assert_eq!(obj.book(50, 60), 1);
    assert_eq!(obj.book(10, 40), 2);
    assert_eq!(obj.book(5, 15), 3);
    assert_eq!(obj.book(5, 10), 3);
    assert_eq!(obj.book(25, 55), 3);
}

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