poj 1716 Integer Intervals

        
//贪心,按区间的终止点（右边的点）从小到大排列，我们每次取区间最右边的点,使这个区间内至少有两个点在s中
#include <iostream>    
#include <algorithm>
using namespace std;
struct node 
{
    int x;int y;
    bool operator<(const node& n)const
    {
        return y<n.y;
    }
}interval[10001];
int res[10001];

int main()
{
    int n,i,j,ans,top=-1;
    cin>>n;
    for(i=0;i<n;i++)
        cin>>interval[i].x>>interval[i].y;
    sort(interval,interval+n);
    for(i=0;i<n;i++)
    {
        ans=0;
        for(j=0;j<=top;j++)
            if(res[j]>=interval[i].x&&res[j]<=interval[i].y)
            {
                ans++;
                if(ans>=2)
                    break;
            }
        if(ans==0)
        {
            res[++top]=interval[i].y-1;
            res[++top]=interval[i].y;    
        }
        else if(ans==1)
            res[++top]=interval[i].y;    
    }
    cout<<top+1<<endl;
    return 0;
}