Time limit 2000/4000/4000/4000 ms. Memory limit 65000/65000/65000/65000 Kb. Question by Arbli Troshani.
Campus Tours for High Schools
Epoka University is organizing Campus Tours for
high schools of Tirana this Tuesday. Each high school though,
can come within a certain time period [ai, bi] only.
Question: You want to find the minimum
number of bus trips so that all high schools are satisfied and
within their planned timeframe.
Input specification The first line of the
input contains the number of schools (n). Each of the following
n lines contains two integers ai and bi
(separated by a space) defining available time frame of the i-th
high school (the school will be happy if the bus takes students
within this time frame) where n is between 1 and 40,000 and
0 ≤ ai ≤ bi ≤ 23.
Output specification First print the
minimum number m of time points on the first line and the integer
values of m time points (separated by spaces)
on the second line.
Sample Input I
3
1 3
2 5
3 6
|
Sample Input II
4
4 7
1 3
2 5
5 6
|
Sample Output I
1
3 |
Sample Output II
2
3 6 |
Explanation: (for Sample 1:)
There are three schools coming. And all schools are
available at three o'clock. One bus is sufficient to
take students from all three schools.
Для отправки решений необходимо выполнить вход.
|