Help!

eveline · #1 01-21-2012, 10:03 AM

Hello!

I'm new here, but for a long time following this forum. I got task for some project to do, but I really don't know how to start. If someone can help me, I would be grateful. I didn't do anything. I don't realize this task and I don't know how to start, I don't know what I need to do in this task, or anything. I need the whole code. If anyone can solve this, please help me, it's an emergency.

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You are given N open intervals on a line (the intervals do not include their endpoints). Your task is to write a program which finds the largest number of intervals that can be chosen so they don't intersect.

INPUT:
The first line of the standard input contains a number N (0<N<=5000), the number of intervals. The next N lines contain two integers li and ri (-10000< li < di <10000) which represent the left and right ends of the interval (1<=i<=N).

OUTPUT:
To the standard output in one line write the number of intervals which can be chosen so that they do not intersect.

Input:
4
-1 1
0 5
2 3
5 9

Output:
3

P.S. The program is required to implement function, which checks whether two intervals have a common point: bool check (int beg1, int end1, int beg2, int end2).I am suffering with this for a long time and I can not resolve it, the task should be solved using the iostream library.

hobbyist · #2 01-27-2012, 06:49 PM

c++ is a bit advanced for me, but I *think* you can use a vector

declare a 2d vector

Code:

std::vector<std::vector<int> > intervals;

add some data

Code:

loop(while input is stored) {
   intervals.push_back(std::vector<int>(2)); // prepare a set of end pts
   // request end pt 1 and end pt 2
   std::cin >> intervals[loop_counter][0] // end pt 1
   std::cin >> intervals[loop_counter][1] // end pt 2
}

I *think* the function would want to check intervals[0][0], intervals[0][1] against the other sets in the vector, so use a loop starting at index pos 1

Code:

for(int i=1; i < intervals.size(); ++i) {
   if(check(intervals[0][0], intervals[0][1], intervals[i][0], intervals[i][1]) == false)
      ++count;
}

oops; forgot the function

Code:

bool check(int s1, int e1, int s2, int e2) {
   return (s2 >= s1 && e2 <= e1);
}

maybe something like that.
HTH