附代码
Source Code

Problem: 1843  User: JiaJunpeng 
Memory: 224K  Time: 63MS 
Language: C++  Result: Accepted 

Source Code 
#include<iostream>
#include<cstdlib>
#include<cstring>
#include<algorithm>
#include<stdio.h>
#include<cmath>
using namespace std;
double xx,yy,l,eps=1e-7;
struct point
{
    double x,y;
    bool operator <(const point &temp)const
    {
         if(fabs((y-yy)*(temp.x-xx)-(x-xx)*(temp.y-yy))<eps)
             return fabs(x-xx)+fabs(y-yy)>fabs(temp.x-xx)+fabs(temp.y-yy);
         return (y-yy)*(temp.x-xx)-(x-xx)*(temp.y-yy)<0;
    }
};
point a[101],stack[101],na[101];
int n,top,ans,cnt,dp[101][101];
double cross(double x1,double y1,double x2,double y2)
{
       return x1*y2-x2*y1;
}
int main()
{
    int i,j,s,p,q;
    scanf("%d",&n);
    a[0].x=a[0].y=xx=yy=0;
    for(i=1;i<=n;i++)
       scanf("%lf%lf",&a[i].x,&a[i].y);
    n++;
    scanf("%lf",&l);
    ans=0;
    na[0]=a[0]; 
    for(i=1;i<=n;i++)
    {
         cnt=1;
         dp[0][0]=1;
         if(ans<1)
            ans=1; 
         if(2*(a[i].x+a[i].y)<=l)
         {
             na[cnt++]=a[i];
             if(ans<2)
                ans=2;
             for(j=1;j<n;j++)
             {
                if(j==i) 
                  continue;
                if(a[j].x<=a[i].x&&2*(a[j].y+a[i].x)<=l)
                    na[cnt++]=a[j];
             }
             sort(na+1,na+cnt);
             for(j=1;j<cnt;j++)
             {
                 dp[0][j]=2;
                 for(s=j+1;s<cnt;s++)
                 {
                     if(fabs(cross(na[s].x,na[s].y,na[j].x,na[j].y))<eps)
                        dp[0][j]++;
                 } 
             }
             for(j=1;j<cnt;j++)
                for(s=j+1;s<cnt;s++)
                {
                     dp[j][s]=2;
                     if(fabs(cross(na[s].x,na[s].y,na[j].x,na[j].y))<eps)
                        continue;
                     for(p=0;p<j;p++)
                     {
                        if(cross(na[s].x-na[p].x,na[s].y-na[p].y,na[j].x-na[p].x,na[j].y-na[p].y)<eps)
                        {
                            if(dp[j][s]<dp[p][j]+1)
                               dp[j][s]=dp[p][j]+1;
                        }
                     } 
                     int value;
                     if(cross(na[0].x-na[j].x,na[0].y-na[j].y,na[s].x-na[j].x,na[s].y-na[j].y)<eps)
                     {
                        value=dp[j][s];
                        for(p=s+1;p<cnt;p++)
                        {
                           if(fabs(cross(na[0].x-na[s].x,na[0].y-na[s].y,na[p].x-na[s].x,na[p].y-na[s].y))<eps)
                              value++;
                        }
                        if(ans<value)
                           ans=value;
                     }
                }
         }   
    }   
    printf("%d\n",ans);  
    return 0;
}