HDU 5130 Signal Interference

题目链接:http://acm.hdu.edu.cn/showproblem.php?pid=5130

转载链接:http://blog.csdn.net/qq_21057881/article/details/51298432

题意: 就是求一个圆和多边形相交的公共面积.
分析:这是参考别人的模板,拿来己用.
代码:

/* Author:GavinjouElephant * Title: * Number: * main meanning： * * * */#include <iostream>using namespace std;#include <cstdio>#include <cmath>#include <cstring>#include <algorithm>#include <sstream>#include <cctype>#include <vector>#include <set>#include <cstdlib>#include <map>#include <queue>//#include<initializer_list>//#include <windows.h>//#include <fstream>//#include <conio.h>#define MaxN 0x7fffffff#define MinN -0x7fffffff#define lson 2*k#define rson 2*k+1typedef long long ll;const int INF=0x3f3f3f3f;const int maxn=1e5+10;#define eps 1e-8int Scan()//读入整数外挂.{    int res = 0, ch, flag = 0;    if((ch = getchar()) == '-')             //判断正负        flag = 1;    else if(ch >= '0' && ch <= '9')           //得到完整的数        res = ch - '0';    while((ch = getchar()) >= '0' && ch <= '9' )        res = res * 10 + ch - '0';    return flag ? -res : res;} void Out(int a)    //输出外挂 {     if(a>9)         Out(a/10);     putchar(a%10+'0'); } struct Point{    double x,y;    Point(double x=0, double y=0):x(x),y(y) {}    void input() { scanf("%lf%lf",&x,&y); }};typedef Point Vector;struct Circle{    Point c;    double r;    Circle(){}    Circle(Point c,double r):c(c),r(r) {}    Point point(double a) { return Point(c.x + cos(a)*r, c.y + sin(a)*r); }    void input() { scanf("%lf%lf%lf",&c.x,&c.y,&r); }};int dcmp(double x) {    if(x < -eps) return -1;    if(x > eps) return 1;    return 0;}template <class T> T sqr(T x) { return x * x;}Vector operator + (Vector A, Vector B) { return Vector(A.x + B.x, A.y + B.y); }Vector operator - (Vector A, Vector B) { return Vector(A.x - B.x, A.y - B.y); }Vector operator * (Vector A, double p) { return Vector(A.x*p, A.y*p); }Vector operator / (Vector A, double p) { return Vector(A.x/p, A.y/p); }bool operator < (const Point& a, const Point& b) { return a.x < b.x || (a.x == b.x && a.y < b.y); }bool operator >= (const Point& a, const Point& b) { return a.x >= b.x && a.y >= b.y; }bool operator <= (const Point& a, const Point& b) { return a.x <= b.x && a.y <= b.y; }bool operator == (const Point& a, const Point& b) { return dcmp(a.x-b.x) == 0 && dcmp(a.y-b.y) == 0; }double Dot(Vector A, Vector B) { return A.x*B.x + A.y*B.y; }double Length(Vector A) { return sqrt(Dot(A, A)); }double Angle(Vector A, Vector B) { return acos(Dot(A, B) / Length(A) / Length(B)); }double Cross(Vector A, Vector B) { return A.x*B.y - A.y*B.x; }Vector VectorUnit(Vector x){ return x / Length(x);}Vector Normal(Vector x) { return Point(-x.y, x.x) / Length(x);}double angle(Vector v) { return atan2(v.y, v.x); }bool OnSegment(Point P, Point A, Point B) {    return dcmp(Cross(A-P,B-P)) == 0 && dcmp(Dot(A-P,B-P)) < 0;}double DistanceToSeg(Point P, Point A, Point B){    if(A == B) return Length(P-A);    Vector v1 = B-A, v2 = P-A, v3 = P-B;    if(dcmp(Dot(v1, v2)) < 0) return Length(v2);    if(dcmp(Dot(v1, v3)) > 0) return Length(v3);    return fabs(Cross(v1, v2)) / Length(v1);}double DistanceToLine(Point P, Point A, Point B){    Vector v1 = B-A, v2 = P-A;    return fabs(Cross(v1,v2)) / Length(v1);}Point DisP(Point A, Point B){    return Length(B-A);}bool SegmentIntersection(Point A,Point B,Point C,Point D) {    return max(A.x,B.x) >= min(C.x,D.x) &&           max(C.x,D.x) >= min(A.x,B.x) &&           max(A.y,B.y) >= min(C.y,D.y) &&           max(C.y,D.y) >= min(A.y,B.y) &&           dcmp(Cross(C-A,B-A)*Cross(D-A,B-A)) <= 0 &&           dcmp(Cross(A-C,D-C)*Cross(B-C,D-C)) <= 0;}Point Zero = Point(0,0);double TriAngleCircleInsection(Circle C, Point A, Point B){    Vector OA = A-C.c, OB = B-C.c;    Vector BA = A-B, BC = C.c-B;    Vector AB = B-A, AC = C.c-A;    double DOA = Length(OA), DOB = Length(OB),DAB = Length(AB), r = C.r;    if(dcmp(Cross(OA,OB)) == 0) return 0;    if(dcmp(DOA-C.r) < 0 && dcmp(DOB-C.r) < 0) return Cross(OA,OB)*0.5;    else if(DOB < r && DOA >= r) {        double x = (Dot(BA,BC) + sqrt(r*r*DAB*DAB-Cross(BA,BC)*Cross(BA,BC)))/DAB;        double TS = Cross(OA,OB)*0.5;        return asin(TS*(1-x/DAB)*2/r/DOA)*r*r*0.5+TS*x/DAB;    }    else if(DOB >= r && DOA < r) {        double y = (Dot(AB,AC)+sqrt(r*r*DAB*DAB-Cross(AB,AC)*Cross(AB,AC)))/DAB;        double TS = Cross(OA,OB)*0.5;        return asin(TS*(1-y/DAB)*2/r/DOB)*r*r*0.5+TS*y/DAB;    }    else if(fabs(Cross(OA,OB)) >= r*DAB || Dot(AB,AC) <= 0 || Dot(BA,BC) <= 0) {        if(Dot(OA,OB) < 0) {            if(Cross(OA,OB) < 0) return (-acos(-1.0)-asin(Cross(OA,OB)/DOA/DOB))*r*r*0.5;            else                 return ( acos(-1.0)-asin(Cross(OA,OB)/DOA/DOB))*r*r*0.5;        }        else                     return asin(Cross(OA,OB)/DOA/DOB)*r*r*0.5;    }    else {        double x = (Dot(BA,BC)+sqrt(r*r*DAB*DAB-Cross(BA,BC)*Cross(BA,BC)))/DAB;        double y = (Dot(AB,AC)+sqrt(r*r*DAB*DAB-Cross(AB,AC)*Cross(AB,AC)))/DAB;        double TS = Cross(OA,OB)*0.5;        return (asin(TS*(1-x/DAB)*2/r/DOA)+asin(TS*(1-y/DAB)*2/r/DOB))*r*r*0.5 + TS*((x+y)/DAB-1);    }}//data segmentPoint p[507],A,B;//data endsint main(){#ifndef ONLINE_JUDGE    freopen("coco.txt","r",stdin);    freopen("lala.txt","w",stdout);#endif    int n,i,j,cs = 1;    double k;    while(scanf("%d%lf",&n,&k)!=EOF)    {        for(i=1;i<=n;i++) p[i].input();        A.input(), B.input(), p[n+1] = p[1];        double D = (2.0*k*k*A.x-2.0*B.x)/(1.0-k*k);        double E = (2.0*k*k*A.y-2.0*B.y)/(1.0-k*k);        double F = (B.x*B.x+B.y*B.y-k*k*(A.x*A.x+A.y*A.y))/(1.0-k*k);        Circle C = Circle(Point(-D*0.5,-E*0.5),sqrt(D*D+E*E-4.0*F)*0.5);        double ans = 0.0;        for(i=1;i<=n;i++)            ans += TriAngleCircleInsection(C, p[i], p[i+1]);        printf("Case %d: %.10f\n",cs++,fabs(ans));    }    return 0;}