LC1109.航班预订统计

思路

• 差分：和ACW797很像，参考那一题即可。

• 注意处理边界的情况，差分数组需要开大一点，因为最后可能会超过范围

  代码

  class Solution {
  public:
    vector<int> corpFlightBookings(vector<vector<int>>& bookings, int n) {
        // 航班编号从1开始
        int n_books = bookings.size();
        vector<int> seats_list(n, 0);
        vector<int> diff(n + 1, 0);
        for (int i = 0; i < n_books; ++i) {
            int begin_pos = bookings[i][0] - 1;
            int end_pos = bookings[i][1] - 1;
            int add_nums = bookings[i][2];
            diff[begin_pos] += add_nums;
            diff[end_pos + 1] -= add_nums;
        }
        for (int i = 0; i < n; ++i) {
            if (i == 0) {
                seats_list[0] = diff[0];
            } else {
                seats_list[i] = seats_list[i - 1] + diff[i];
            }
        }
        return seats_list;
    }
  };