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Corporate Flight Bookings⚓︎

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Description⚓︎

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

You are given an array of flight bookings bookings, where bookings[i] = [first_i, last_i, seats_i] represents a booking for flights first_i through last_i (inclusive ) with seats_i 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:

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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:

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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]

Constraints:

  • 1 <= n <= 2 * 10^4
  • 1 <= bookings.length <= 2 * 10^4
  • bookings[i].length == 3
  • 1 <= first_i <= last_i <= n
  • 1 <= seats_i <= 10^4

Solution⚓︎

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class Solution {
public:
    vector<int> corpFlightBookings(vector<vector<int>>& bookings, int n) {
        vector<int> counters(n + 2);
        for (const auto& booking : bookings) {
            counters[booking[0]] += booking[2];
            counters[booking[1] + 1] -= booking[2];
        }

        for (int i = 1; i < counters.size(); i++) {
            counters[i] += counters[i - 1];
        }

        vector<int> res(n);
        for (int i = 0; i < n; i++) {
            res[i] = counters[i + 1];
        }
        return res;
    }
};

Another way of writing:

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class Solution {
public:
    vector<int> corpFlightBookings(vector<vector<int>>& bookings, int n) {
        vector<int> counters(n, 0);

        for (const auto& booking : bookings) {
            counters[booking[0] - 1] += booking[2];
            if (booking[1] < n)
                counters[booking[1]] -= booking[2];
        }

        for (int i = 1; i < n; i++) {
            counters[i] += counters[i - 1];
        }

        return counters;
    }
};