bzoj 2300 动态维护上凸壳（不支持删除）

新技能GET。

用set保存点，然后只需要找前趋和后继就可以动态维护了。

 /**************************************************************
     Problem: 2300
     User: idy002
     Language: C++
     Result: Accepted
     Time:556 ms
     Memory:4824 kb
 ****************************************************************/

 #include <cstdio>
 #include <cmath>
 #include <set>
 #define N 100010
 #define line(a,b) ((b)-(a))
 using namespace std;

 struct Job {
     int opt, v;
     double ans;
 };
 struct Vector {
     int x, y;
     void read() { scanf( "%d%d", &x, &y ); }
     Vector(){}
     Vector( int x, int y ):x(x),y(y){}
     Vector operator+( const Vector &b ) const { return Vector(x+b.x,y+b.y); }
     Vector operator-( const Vector &b ) const { return Vector(x-b.x,y-b.y); }
     int operator^( const Vector &b ) const { return x*b.y-y*b.x; }
     double len() { return sqrt(x*x+y*y); }
     bool operator<( const Vector &b ) const {
         return x<b.x || (x==b.x && y<b.y);
     }
 };
 typedef Vector Point;

 int n, m, q;
 Point pts[N];
 set<Point> cvx;
 Job job[N+N];
 bool done[N];
 double ans;

 bool onleft( const Point &a, const Point &b, const Point &c ) {
     return (line(a,b) ^ line(a,c)) > ;
 }
 void insert( const Point &p ) {
     set<Point>::iterator prv, nxt, prev, next;
     prv = nxt = cvx.upper_bound( p );
     --prv;
     if( !onleft(*nxt,p,*prv) ) return;
     while( prv!=cvx.begin() ) {
         prev = prv;
         --prev;
         if( !onleft(p,*prv,*prev) ) {
             ans += line(*prev,*nxt).len()-line(*prev,*prv).len()-line(*prv,*nxt).len();
             cvx.erase(prv);
         } else break;
         prv = prev;
     }
     while( nxt!=cvx.end() ) {
         next = nxt;
         ++next;
         if( next==cvx.end() ) break;
         if( !onleft(*next,*nxt,p) ) {
             ans += line(*prv,*next).len()-line(*prv,*nxt).len()-line(*nxt,*next).len();
             cvx.erase(nxt);
         } else break;
         nxt = next;
     }
     cvx.insert( p );
     ans += line(*prv,p).len()+line(*nxt,p).len()-line(*prv,*nxt).len();
 }
 int main() {
     scanf( "%d", &n );
     pts[].read();
     scanf( "%d", &m );
     for( int i=; i<=m; i++ )
         pts[i].read();
     scanf( "%d", &q );
     for( int i=; i<=q; i++ ) {
         scanf( "%d", &job[i].opt );
         if( job[i].opt== ) {
             scanf( "%d", &job[i].v );
             done[job[i].v] = true;
         }
     }
     cvx.insert( Point(,) );
     cvx.insert( pts[] );
     cvx.insert( Point(n,) );
     ans += line(Point(,),pts[]).len() + line(Point(n,),pts[]).len();
     for( int i=; i<=m; i++ )
         if( !done[i] ) insert( pts[i] );
     for( int i=q; i>=; i-- ) {
         if( job[i].opt== ) {
             insert( pts[job[i].v] );
         } else {
             job[i].ans = ans;
         }
     }
     for( int i=; i<=q; i++ )
         if( job[i].opt== )
             printf( "%.2lf\n", job[i].ans );
 }