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  • HDU 1147 Pick-up sticks

    题解:每放一根棍子,都判断一下它与它前面的且在顶端的棍子是否相交,相交的话则将相应的棍子从解空间中除去。

    #include <cstdio> 
    const double eps=1e-14;  
    const int maxn=1e5+10;  
    struct node{double x1,y1,x2,y2;int w;}e[maxn],f[maxn];  
    double cross(double x1,double y1,double x2,double y2){return x1*y2-x2*y1;}  
    int find(node a,node b){  
        double c[4];  
        c[0]=cross(a.x2-a.x1,a.y2-a.y1,b.x1-a.x1,b.y1-a.y1);  
        c[1]=cross(a.x2-a.x1,a.y2-a.y1,b.x2-a.x1,b.y2-a.y1);  
        c[2]=cross(b.x2-b.x1,b.y2-b.y1,a.x1-b.x1,a.y1-b.y1);  
        c[3]=cross(b.x2-b.x1,b.y2-b.y1,a.x2-b.x1,a.y2-b.y1);  
        if(c[0]*c[1]<=0&&c[2]*c[3]<=0)return 1;  
        return 0;  
    }  
    int main(){  
        int n;  
        while(scanf("%d",&n)!=EOF){  
            if(n==0)break;  
            int i,j,k,p,q;  
            for(i=0;i<n;i++){  
                scanf("%lf%lf%lf%lf",&e[i].x1,&e[i].y1,&e[i].x2,&e[i].y2);  
                e[i].w=i+1;  
            }p=0;  
            for(i=0;i<n;i++){  
                q=0;  
                for(j=0;j<p;j++)  
                    if(!find(e[i],f[j]))f[q++]=f[j];  
                f[q++]=e[i];  
                p=q;  
            }  
            printf("Top sticks: %d",f[0].w);  
            for(i=1;i<p;i++)printf(", %d",f[i].w);  
            printf(".
    ");  
        }  
        return 0;  
    } 
    
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  • 原文地址:https://www.cnblogs.com/forever97/p/3650034.html
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