Luogu-2521 [HAOI2011]防线修建

标签：int   bre   iterator   tor   clu   -o   ++   ase   insert   

倒过来处理所有询问，就变成了一道动态凸包的裸题

吐槽一下这道题只要维护上凸壳就好了，我zz了没好好看题打了两个2333

// luogu-judger-enable-o2
#include<set>
#include<cmath>
#include<cstdio>
#include<cstring>
#include<algorithm>
#define rp (*r)
#define lp (*l)
#define rrp (*rr)
#define llp (*ll)
using namespace std;
const int maxn=1e6+100;
struct Vector{
    double x,y;
    Vector(double xx=0,double yy=0){
        x=xx,y=yy;
    }
};
struct Point{
    double x,y;
    Point(double xx=0,double yy=0){
        x=xx,y=yy;
    }
    bool operator < (Point a) const{
        return x==a.x?y<a.y:x<a.x;
    }
}a[maxn],b[maxn],tmp[maxn];
int dcmp(double x){return fabs(x)<1e-9?0:x>0;}
bool operator == (Point a,Point b){return a.x==b.x&&a.y==b.y;}
Vector operator - (Point a,Point b){return Vector(a.x-b.x,a.y-b.y);}
double operator * (Vector a,Vector b){return a.x*b.y-a.y*b.x;}
double dot(Vector a,Vector b){return a.x*b.x+a.y*b.y;}
double len(Vector a){return sqrt(dot(a,a));}
int m,s,t,ms[maxn],err[maxn],c[maxn],n;
double pp,x,y,ans,an[maxn];
set<Point>u,d;
void tb(Point *p,int &n){
    if(n==1) return;
    sort(p+1,p+n+1);
    tmp[1]=p[1];
    int m=1;
    for(int i=2;i<=n;i++){
        while(m>1&&(tmp[m]-tmp[m-1])*(p[i]-tmp[m-1])<=0)
            m--;
        tmp[++m]=p[i];
    }
    for(int i=1;i<m;i++)
        d.insert(tmp[i]),ans+=len(tmp[i+1]-tmp[i]);
    d.insert(tmp[m]);
    int k=m;
    for(int i=n-1;i>=1;i--){
        while(m>k&&(tmp[m]-tmp[m-1])*(p[i]-tmp[m-1])<=0)
            m--;
        tmp[++m]=p[i];
    }
    for(int i=k;i<m;i++)
        u.insert(tmp[i]),ans+=len(tmp[i+1]-tmp[i]);
    u.insert(tmp[m]);
    ans-=pp;
}
void uinsert(Point p){
    set<Point>::iterator l,r,ll,rr;
    r=u.lower_bound(p);
    l=--r,r++;
//  printf("%lf %lf\n%lf %lf\n",lp.x,lp.y,rp.x,rp.y);
    if((p-lp)*(rp-lp)>0) return;
    ans=ans-len(rp-lp)+len(p-lp)+len(p-rp);
    while(l!=u.begin()){
        ll=--l,l++;
//      printf("%lf %lf\n",llp.x,llp.y);
        if((lp-llp)*(p-llp)<0) break;
//      printf("%lf %lf %lf\n",len(p-lp),len(lp-llp),len(p-llp));
        ans=ans-len(p-lp)-len(lp-llp)+len(p-llp);
        u.erase(l);
        l=ll;
    }
    rr=++r,r--;
    while(rr!=u.end()){
//      printf("%lf %lf\n",rrp.x,rrp.y);
        if((rrp-p)*(rp-p)>0) break;
//      printf("%lf %lf %lf\n",len(rp-p),len(rrp-rp),len(rrp-p));
        ans=ans-len(rp-p)-len(rrp-rp)+len(rrp-p);
        u.erase(r);
        r=rr;
        rr=++r,r--;
    }
    u.insert(p);
}
/*
void dinsert(Point p){
    set<Point>::iterator l,r,ll,rr;
    r=d.lower_bound(p);
    l=--r,r++;
    if((p-lp)*(rp-lp)<0) return;
    ans=ans-len(rp-lp)+len(p-lp)+len(p-rp);
    while(l!=d.begin()){
        ll=--l,l++;
        if((lp-llp)*(p-llp)>0) break;
        ans=ans-len(lp-p)-len(llp-lp)+len(llp-p);
        u.erase(l);
        l=ll;
    }
    rr=++r,r--;
    while(rr!=d.end()){
        if((rrp-p)*(rp-p)>0) break;
        ans=ans-len(rp-p)-len(rrp-rp)+len(rrp-p);
        u.erase(r);
        r=rr;
        rr=++r,r--;
    }
    d.insert(p);
}
*/
int main(){
    scanf("%lf%lf%lf",&pp,&x,&y);
    scanf("%d",&m);
    for(int i=1;i<=m;i++)
        scanf("%lf%lf",&b[i].x,&b[i].y);
    scanf("%d",&t);
    for(int i=1;i<=t;i++){
        scanf("%d",&ms[i]);
        if(ms[i]==1){
            scanf("%d",&c[i]);
            err[c[i]]=1;
        }
    }
    a[1].x=a[1].y=a[2].y=0;
    a[2].x=pp,a[3].x=x,a[3].y=y;
    n=3;
    for(int i=1;i<=m;i++)
        if(!err[i])
            a[++n]=b[i];
    tb(a,n);
    for(int i=t;i>=1;i--){
        if(ms[i]==1)
            uinsert(b[c[i]]);//,dinsert(b[c[i]]);
        else
            an[i]=ans;
    }
    for(int i=1;i<=t;i++)
        if(ms[i]==2)
            printf("%.2lf\n",an[i]);
    return 0;
}

Luogu-2521 [HAOI2011]防线修建

标签：int   bre   iterator   tor   clu   -o   ++   ase   insert   

原文地址：https://www.cnblogs.com/nianheng/p/10004598.html