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  • zoj2589

    是cf933C的升级版。
    平面图欧拉定理。over!
    f=e-v+c+1
    c是联通块,相交才视为一块。
    e是圆弧数,v是顶点数。

    #include <bits/stdc++.h>
    #define pii pair<int,int>
    #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
    ",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;}
    struct circle{
        point o; db r;
        void scan(){o.scan(); scanf("%lf",&r);}
        int inside(point k){return cmp(r,o.dis(k));}
    };
    int checkposCC(circle k1,circle k2){// 返回两个圆的公切线数量
        if (cmp(k1.r,k2.r)==-1) swap(k1,k2);
        db dis=k1.o.dis(k2.o);  int w1=cmp(dis,k1.r+k2.r),w2=cmp(dis,k1.r-k2.r);
        if (w1>0) return 4; else if (w1==0) return 3; else if (w2>0) return 2;
        else if (w2==0) return 1; else return 0;
    }
    vector<point> getCC(circle k1,circle k2){// 沿圆 k1 逆时针给出 , 相切给出两个
        int pd=checkposCC(k1,k2); if (pd==0||pd==4) return {};
        db a=(k2.o-k1.o).abs2(),cosA=(k1.r*k1.r+a-k2.r*k2.r)/(2*k1.r*sqrt(max(a,(db)0.0)));
        db b=k1.r*cosA,c=sqrt(max((db)0.0,k1.r*k1.r-b*b));
        point k=(k2.o-k1.o).unit(),m=k1.o+k*b,del=k.turn90()*c;
        return {m-del,m+del};
    }
    int t,n,vis[55];
    circle c[55];
    set<point> s;
    vector<point> v;
    set<pii> st;
    void slove(int x){
        vis[x]=1;
        for(auto p:st){
            for(int i=0;i<n;i++){
                if(vis[p.fi]||vis[p.se]){
                    vis[p.fi]=vis[p.se]=1;
                    break;
                }
            }
        }
    }
    int main(){
        scanf("%d",&t);
        while (t--) {
            v.clear();
            s.clear();
            st.clear();
            memset(vis,0, sizeof(vis));
            scanf("%d", &n);
            for (int i = 0; i < n; i++) {
                scanf("%lf%lf%lf", &c[i].o.x, &c[i].o.y, &c[i].r);
            }
            int p = 0;
            for (int i = 0; i < n; i++) {
                for (int j = i + 1; j < n; j++) {
                    v = getCC(c[i], c[j]);
                    for (auto t:v)s.insert(t);
                    if(!v.empty())
                        st.insert(pii(i,j));
                }
            }
            for(int i=0;i<n;i++){
                if(!vis[i]) {
                    slove(i);
                    p++;
                }
            }
            int e=0,v;
            v = s.size();
            for (int i = 0; i < n; i++) {
                for (auto x:s) {
                    if (c[i].inside(x) == 0)
                        e++;
                }
            }
            cout << e - v + 1 + p << endl;
        }
    }
    
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  • 原文地址:https://www.cnblogs.com/MXang/p/11329956.html
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