出于某种不可抗力我翻了一下以前绿名时打的div2,然后插旗:这种傻逼div2我现在不是随手ak吗? 然后就没有然后了
给一个凸包,一开始固定两个点,每次拆下一个点(取消固定),待稳定后再固定另外一个点。
支持查询第几个点的坐标。
首先求凸包重心,全部划分成三角形那样子。
考虑一次旋转操作,其实是将重心旋转到了固定点的正下方。
那么在知道了每个点相对于重心的向量后,这其实蛮好求的。
同样,重心每次旋转的角度也容易知道。
所以我们翻过来考虑,维护重心坐标和旋转角度,对于一个查询,我们用它的相对位置*角度+重心即可。
很好的一道题。
有点神志不清调了好久
#include <bits/stdc++.h> #define mp make_pair #define fi first #define se second #define pb push_back using namespace std; typedef double db; const db eps=1e-6; const db pi=acos(-1); int sign(db k){ if (k>eps) return 1; else if (k<-eps) return -1; return 0; } int cmp(db k1,db k2){return sign(k1-k2);} int inmid(db k1,db k2,db k3){return sign(k1-k3)*sign(k2-k3)<=0;}// k3 在 [k1,k2] 内 struct point{ db x,y; point operator + (const point &k1) const{return (point){k1.x+x,k1.y+y};} point operator - (const point &k1) const{return (point){x-k1.x,y-k1.y};} point operator * (db k1) const{return (point){x*k1,y*k1};} point operator / (db k1) const{return (point){x/k1,y/k1};} int operator == (const point &k1) const{return cmp(x,k1.x)==0&&cmp(y,k1.y)==0;} // 逆时针旋转 point turn(db k1){return (point){x*cos(k1)-y*sin(k1),x*sin(k1)+y*cos(k1)};} point turn90(){return (point){-y,x};} bool operator < (const point k1) const{ int a=cmp(x,k1.x); if (a==-1) return 1; else if (a==1) return 0; else return cmp(y,k1.y)==-1; } db abs(){return sqrt(x*x+y*y);} db abs2(){return x*x+y*y;} db dis(point k1){return ((*this)-k1).abs();} point unit(){db w=abs(); return (point){x/w,y/w};} void scan(){double k1,k2; scanf("%lf%lf",&k1,&k2); x=k1; y=k2;} void print(){printf("%.11lf %.11lf\n",x,y);} db getw(){return atan2(y,x);} point getdel(){if (sign(x)==-1||(sign(x)==0&&sign(y)==-1)) return (*this)*(-1); else return (*this);} int getP() const{return sign(y)==1||(sign(y)==0&&sign(x)==-1);} }; int inmid(point k1,point k2,point k3){return inmid(k1.x,k2.x,k3.x)&&inmid(k1.y,k2.y,k3.y);} db cross(point k1,point k2){return k1.x*k2.y-k1.y*k2.x;} db dot(point k1,point k2){return k1.x*k2.x+k1.y*k2.y;} db rad(point k1,point k2){return atan2(cross(k1,k2),dot(k1,k2));} // -pi -> pi int compareangle (point k1,point k2){//极角排序+ return k1.getP()<k2.getP()||(k1.getP()==k2.getP()&&sign(cross(k1,k2))>0); } point proj(point k1,point k2,point q){ // q 到直线 k1,k2 的投影 point k=k2-k1;return k1+k*(dot(q-k1,k)/k.abs2()); } point reflect(point k1,point k2,point q){return proj(k1,k2,q)*2-q;} int clockwise(point k1,point k2,point k3){// k1 k2 k3 逆时针 1 顺时针 -1 否则 0 return sign(cross(k2-k1,k3-k1)); } int checkLL(point k1,point k2,point k3,point k4){// 求直线 (L) 线段 (S)k1,k2 和 k3,k4 的交点 return cmp(cross(k3-k1,k4-k1),cross(k3-k2,k4-k2))!=0; } point getLL(point k1,point k2,point k3,point k4){ db w1=cross(k1-k3,k4-k3),w2=cross(k4-k3,k2-k3); return (k1*w2+k2*w1)/(w1+w2); } int intersect(db l1,db r1,db l2,db r2){ if (l1>r1) swap(l1,r1); if (l2>r2) swap(l2,r2); return cmp(r1,l2)!=-1&&cmp(r2,l1)!=-1; } int checkSS(point k1,point k2,point k3,point k4){ return intersect(k1.x,k2.x,k3.x,k4.x)&&intersect(k1.y,k2.y,k3.y,k4.y)&& sign(cross(k3-k1,k4-k1))*sign(cross(k3-k2,k4-k2))<=0&& sign(cross(k1-k3,k2-k3))*sign(cross(k1-k4,k2-k4))<=0; } db disSP(point k1,point k2,point q){ point k3=proj(k1,k2,q); if (inmid(k1,k2,k3)) return q.dis(k3); else return min(q.dis(k1),q.dis(k2)); } db disSS(point k1,point k2,point k3,point k4){ if (checkSS(k1,k2,k3,k4)) return 0; else return min(min(disSP(k1,k2,k3),disSP(k1,k2,k4)),min(disSP(k3,k4,k1),disSP(k3,k4,k2))); } int onS(point k1,point k2,point q){return inmid(k1,k2,q)&&sign(cross(k1-q,k2-k1))==0;} point Centroid(vector<point> v){ point ans={0,0};db S=0; for(int i=1;i<v.size()-1;i++){ db s = fabs(cross(v[i]-v[0],v[i+1]-v[0])); ans = ans+(v[0]+v[i]+v[i+1])*s/3; S+=s; } //S!=0 return ans/S; } struct circle{ point o; db r; void scan(){o.scan(); scanf("%lf",&r);} int inside(point k){return cmp(r,o.dis(k));} }; struct line{ // p[0]->p[1] point p[2]; line(point k1,point k2){p[0]=k1; p[1]=k2;} point& operator [] (int k){return p[k];} int include(point k){return sign(cross(p[1]-p[0],k-p[0]))>0;} point dir(){return p[1]-p[0];} line push(){ // 向外 ( 左手边 ) 平移 eps const db eps = 1e-6; point delta=(p[1]-p[0]).turn90().unit()*eps; return {p[0]-delta,p[1]-delta}; } }; point getLL(line k1,line k2){return getLL(k1[0],k1[1],k2[0],k2[1]);} int n,q,b[10005]; vector<point> p;point o; db ang=0; int main(){ scanf("%d%d",&n,&q); p.resize(n); for(int i=0;i<n;i++)scanf("%lf%lf",&p[i].x,&p[i].y); o=Centroid(p); // o.print(); for(int i=0;i<n;i++)p[i]=p[i]-o; int op,f,t,a1=0,a2=1;b[0]=b[1]=1; while (q--){ scanf("%d",&op); if(op==1){ scanf("%d%d",&f,&t); f--;t--; b[f]--; if(b[f]==0){ int otr = (f==a1?a2:a1); point tmp = o+p[otr].turn(ang);//旋转点 // tmp.print(); db jiao = rad(o-tmp,point{0,-1.0}); // printf("%.11f\n",jiao); // printf("%.11f\n",p[otr].abs()); o=tmp+(point){0,-1.0}*p[otr].abs(); ang+=jiao; } // o.print(); b[t]++; if(f==a1)a1=t;else a2=t; }else{ scanf("%d",&f); f--; point tmp=o+p[f].turn(ang); tmp.print(); } } }