動機

太久沒打真的會忘記 這是prefix sum阿

Problem

There are n flights that are labeled from 1 to n.

You are given an array of flight bookings bookings, where bookings[i] = [firsti, lasti, seatsi] represents a booking for flights firsti through lasti (inclusive) with seatsi seats reserved for each flight in the range.

Return an array answer of length n, where answer[i] is the total number of seats reserved for flight i.

 

Example 1:

Input: bookings = [[1,2,10],[2,3,20],[2,5,25]], n = 5Output: [10,55,45,25,25]Explanation:Flight labels:        1   2   3   4   5Booking 1 reserved:  10  10Booking 2 reserved:      20  20Booking 3 reserved:      25  25  25  25Total seats:         10  55  45  25  25Hence, answer = [10,55,45,25,25]

Example 2:

Input: bookings = [[1,2,10],[2,2,15]], n = 2Output: [10,25]Explanation:Flight labels:        1   2Booking 1 reserved:  10  10Booking 2 reserved:      15Total seats:         10  25Hence, answer = [10,25]

 

Constraints:

  • 1 <= n <= 2 * 104
  • 1 <= bookings.length <= 2 * 104
  • bookings[i].length == 3
  • 1 <= firsti <= lasti <= n
  • 1 <= seatsi <= 104

Sol

class Solution:
    def corpFlightBookings(self, bookings: List[List[int]], n: int) -> List[int]:
        res = [0] * (n+1)
        for first, last, num in bookings:
            res[first-1] += num
            res[last] -= num
        for i in range(1, len(res)):
            res[i] += res[i-1]
        return res[:-1]