32. Corporate Flight Bookings

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

Example 2:

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

Solution: (Update Range Query in O(1) )

Approach:

image

class Solution
{
public:
    vector<int> corpFlightBookings(vector<vector<int>> &bookings, int n)
    {
        vector<int> res(n + 2);
        vector<int> arr(n, 0);
        for (int i = 0; i < bookings.size(); i++)
        {
            int start = bookings[i][0];
            int end = bookings[i][1];
            int price = bookings[i][2];

            res[start] += price;
            res[end + 1] -= price;
        }

        int count = 0;

        for (int i = 0; i < n; i++)
        {
            count += res[i + 1];

            arr[i] = count;
        }

        return arr;
    }
};

Time Complexity: O(n)