bzoj1007[HNOI2008]水平可见直线

 1 #include <cstdio>
 2 #include <algorithm>
 3 #include <cstring>
 4 #include <cmath>
 5 #define inc(i,j,k) for(int i=j;i<=k;i++)
 6 #define eps 1e-8
 7 using namespace std;
 8 
 9 struct nd{
10     int a,b,id;
11     bool operator < (const nd& x)const{
12         if(a!=x.a)return a<x.a; return b<x.b;
13     }
14 };
15 double solve(nd a,nd b){
16     return (double)(a.b-b.b)/(double)(b.a-a.a);
17 }
18 nd nds[100000],s[100000]; int ans[100000],n,tp;
19 int main(){
20     scanf("%d",&n);inc(i,1,n)scanf("%d",&nds[i].a),scanf("%d",&nds[i].b),nds[i].id=i; sort(nds+1,nds+1+n);
21     tp=1;s[tp]=nds[1];ans[tp]=nds[1].id;
22     inc(i,2,n){
23         if(nds[i].a-s[tp].a==0)tp--;
24         while(tp>=2&&solve(s[tp-1],s[tp])>=solve(s[tp],nds[i]))tp--;
25         s[++tp]=nds[i]; ans[tp]=nds[i].id;
26     }
27     sort(ans+1,ans+1+tp);inc(i,1,tp)printf("%d ",ans[i]);
28     return 0;
29 }