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）

1 /*#include
     
        2 #define N 100005  3 #define LL long long   4 #define eps 1e-8  5 #define double long double  6 using namespace std;  7 inline int ra()  8 {  9     int x=0,f=1; char ch=getchar(); 10     while (ch<'0' || ch>'9') {if (ch=='-') f=-1; ch=getchar();} 11     while (ch>='0' && ch<='9') {x=x*10+ch-'0'; ch=getchar();} 12     return x*f; 13 } 14 const double inf=1e15; 15 int n,cnt,tot,L,R,ans[N],num,orz; 16 struct data_in{int k,b; int id;}q[N]; 17 struct point{double x,y;}; 18 struct line{ 19     point a,b; double angle; int id; 20     void print(){ 21         printf("%.1lf   %.1lf   %.1lf   %.1lf\n",a.x,a.y,b.x,b.y); 22     } 23 }l[N],s[N]; 24 double operator * (point a, point b){ 25     return a.x*b.y-a.y*b.x; 26 } 27 point operator - (point a, point b){ 28     point t; t.x=a.x-b.x; t.y=a.y-b.y; return t; 29 } 30 bool operator < (line a, line b){ 31     if (a.angle==b.angle) return (b.b-a.a)*(a.b-a.a)>=0; 32     return a.angle
      
       109 #include
       
        110 #define N 100005111 #define eps 1e-8112 using namespace std;113 int n,top;114 int ans[N];115 struct line{116     int k,b,id;117     friend bool operator < (line a, line b){118         if (a.k==b.k) return a.b
        
         inter(a,t);128 }129 int main()130 {131     scanf("%d",&n);132     for (int i=1; i<=n; i++) scanf("%d",&c[i].b);133     for (int i=1; i<=n; i++) scanf("%d",&c[i].k);134     for (int i=1; i<=n; i++) c[i].id=i;135     sort(c+1,c+n+1); top=1;136     for (int i=2; i<=n; i++)137     {138         if (c[i].k!=c[i-1].k || (c[i].k==c[i-1].k && c[i].b==c[i-1].b))139             top++;140         c[top]=c[i];141     }142     n=top; top=0;143     q[++top]=c[1]; ans[1]=c[1].id;144     for (int i=2; i<=n; i++)145     {146         while (top>=1 && inter(q[top],c[i])<-eps) top--;147         while (top>=2 && jud(q[top-1],q[top],c[i])) top--;148         q[++top]=c[i]; ans[top]=c[i].id;149     }150     printf("%d\n",top);151     sort(ans+1,ans+top+1);152     for (int i=1; i<=top; i++)153     {154         printf("%d",ans[i]);155         if (i!=top) printf(" ");156     }157 //    while (1);158     return 0;159 }