bzoj 3190: [JLOI2013]赛车

这个题半平面交很显然了，都直接给出直线了有木有！！？？答案就是交出来的（分段函数）凸壳有几块就行。。有相等什么的情况特别恶心。

然而本蒟蒻直接上的模板还是错了。。。跪（不知道为什么）

/*#include<bits/stdc++.h>
#define N 100005
#define LL long long 
#define eps 1e-8
#define double long double
using namespace std;
inline int ra()
{
    int x=0,f=1; char ch=getchar();
    while (ch<'0' || ch>'9') {if (ch=='-') f=-1; ch=getchar();}
    while (ch>='0' && ch<='9') {x=x*10+ch-'0'; ch=getchar();}
    return x*f;
}
const double inf=1e15;
int n,cnt,tot,L,R,ans[N],num,orz;
struct data_in{int k,b; int id;}q[N];
struct point{double x,y;};
struct line{
    point a,b; double angle; int id;
    void print(){
        printf("%.1lf   %.1lf   %.1lf   %.1lf\n",a.x,a.y,b.x,b.y);
    }
}l[N],s[N];
double operator * (point a, point b){
    return a.x*b.y-a.y*b.x;
}
point operator - (point a, point b){
    point t; t.x=a.x-b.x; t.y=a.y-b.y; return t;
}
bool operator < (line a, line b){
    if (a.angle==b.angle) return (b.b-a.a)*(a.b-a.a)>=0;
    return a.angle<b.angle;
}
bool operator == (point a, point b){
    return a.x==b.x && a.y==b.y;
}
point intersection(line a, line b)
{
    point ans; double k1,k2,t;
    k1=(b.a-a.a)*(a.b-a.a);
    k2=(a.b-a.a)*(b.b-a.a);
    t=k1/(k1+k2);
    ans.x=b.a.x+(b.b.x-b.a.x)*t;
    ans.y=b.a.y+(b.b.y-b.a.y)*t;
    return ans;
}
bool jud(line a, line b, line t)
{
    point p=intersection(a,b);
//    printf("%lf  %lf",p.x,p.y);while(1);
    return (t.a-p)*(t.b-p)<0;
}
void half_plane_intersection()
{
    for (int i=1; i<=cnt; i++)
        if ((l[i].angle!=l[i-1].angle) || (l[i].angle==l[i-1].angle && l[i].a==l[i-1].a && l[i].b==l[i-1].b)) l[++tot]=l[i];
//    for (int i=1; i<=tot; i++) l[i].print();
    L=1; R=0; s[++R]=l[1]; s[++R]=l[2];
//    cout<<jud(l[1],l[2],l[3]);
    for (int i=3; i<=tot; i++)
    {
        if (l[i].a==l[i-1].a && l[i].b==l[i-1].b) {s[++R]=l[i]; continue;}
        while (L<R && jud(s[R],s[R-1],l[i])) R--;
        while (L<R && jud(s[L],s[L+1],l[i])) L++;
        s[++R]=l[i];
    }
    while (L<R && jud(s[R],s[R-1],s[L])) R--;
    while (L<R && jud(s[L],s[L+1],s[R])) L++;
}
bool cmp(data_in a, data_in b)
{
    if (a.k==b.k) return a.b<b.b;
    return a.k<b.k;
}
int main()
{
    n=ra();
    for (int i=1; i<=n; i++) q[i].b=ra();
    for (int i=1; i<=n; i++) q[i].k=ra();
    for (int i=1; i<=n; i++) q[i].id=i;
    sort(q+1,q+n+1,cmp);
    for (int i=1; i<=n; i++)
        if (q[i].k!=q[i-1].k || (q[i].k==q[i-1].k && q[i].b==q[i-1].b)) q[++orz]=q[i];
    for (int i=1; i<=orz; i++)
    {
        l[++cnt].a.x=0; l[cnt].a.y=q[i].b;
        l[cnt].b.x=2; l[cnt].b.y=2*q[i].k+q[i].b;
        l[cnt].id=q[i].id;
    }
    l[++cnt].a.x=-1; l[cnt].a.y=inf; l[cnt].b.x=-1; l[cnt].b.y=-1;
    l[++cnt].a.x=-1; l[cnt].a.y=-1; l[cnt].b.x=inf; l[cnt].b.y=-1;
    for (int i=1; i<=cnt; i++)
        l[i].angle=atan2(l[i].b.y-l[i].a.y,l[i].b.x-l[i].a.x);
    sort(l+1,l+cnt+1);
    half_plane_intersection();
    for (int i=L; i<=R; i++)
        if (s[i].id) ans[++num]=s[i].id;
    sort(ans+1,ans+num+1);
    cout<<num<<endl;
    for (int i=1; i<=num; i++)
    {
        printf("%d",ans[i]);
        if (i!=num) printf(" ");
    }
    return 0;
}*/

#include<cstdio>
#include<algorithm>
#define N 100005
#define eps 1e-8
using namespace std;
int n,top;
int ans[N];
struct line{
    int k,b,id;
    friend bool operator < (line a, line b){
        if (a.k==b.k) return a.b<b.b;
        return a.k<b.k;
    }
    friend double inter(line a, line b){
        return (double)(a.b-b.b)/(b.k-a.k);
    }
}c[N],q[N];
bool jud(line a, line b, line t)
{
    return inter(a,b)>inter(a,t);
}
int main()
{
    scanf("%d",&n);
    for (int i=1; i<=n; i++) scanf("%d",&c[i].b);
    for (int i=1; i<=n; i++) scanf("%d",&c[i].k);
    for (int i=1; i<=n; i++) c[i].id=i;
    sort(c+1,c+n+1); top=1;
    for (int i=2; i<=n; i++)
    {
        if (c[i].k!=c[i-1].k || (c[i].k==c[i-1].k && c[i].b==c[i-1].b))
            top++;
        c[top]=c[i];
    }
    n=top; top=0;
    q[++top]=c[1]; ans[1]=c[1].id;
    for (int i=2; i<=n; i++)
    {
        while (top>=1 && inter(q[top],c[i])<-eps) top--;
        while (top>=2 && jud(q[top-1],q[top],c[i])) top--;
        q[++top]=c[i]; ans[top]=c[i].id;
    }
    printf("%d\n",top);
    sort(ans+1,ans+top+1);
    for (int i=1; i<=top; i++)
    {
        printf("%d",ans[i]);
        if (i!=top) printf(" ");
    }
//    while (1);
    return 0;
}