51nod 1133 Non-overlapping line segments

There are N line segments on the X-axis, and each line segment has a start point S and an end point E. The maximum number of non-overlapping line segments that can be selected. (Note: The starting point or the ending point overlaps, and it is not counted as overlapping).

For example: [1 5][2 3][3 6], you can choose [2 3][3 6], these two line segments do not overlap each other.

Input

Line 1: 1 number N, number of line segments (2 <= N <= 10000) Line 2 - N + 1: 2 numbers per line, start and end points of line segments (-10^9 <= S,E <= 10^9)

Output

Output the maximum number of line segments that can be selected.

Input example

3 1 5 2 3 3 6

Output example

2

Sort in ascending order by end point and traverse directly

Note: The purpose of the question is to ask how many non-overlapping line segments there are, rather than how many pairs of non-overlapping line segments.

#include <iostream>
#include <algorithm>
#include <cstring>
#include <map>
using namespace std;
struct Why
{
    int a;
    int b;
}A[10005];
int cmp(Why x,Why y)
{
    if(x.b!=y.b)
    return x.b<y.b;
}
int N,years;
intmain()
{
   ios::sync_with_stdio(false);
   cin>>N;
   for(int i=0;i<N;i++)
    cin>>A[i].a>>A[i].b;
   sort(A,A+N,cmp);
   int end=A[0].b,t=0;
    for(int i=1;i<N;i++)
    {
        if(A[i].a>=end&&t==0)
        {
            end=A[i].b;
            years=2;
            t=1;
        }
        if(A[i].a>=end&&t==1)
        {
            years++;
            end=A[i].b;
        }
    }
    cout<<ans<<endl;
    return 0;
}