HDU 4637 Rain on your Fat brother

来源：互联网发布：c二维数组初始化为0 编辑：程序博客网时间：2024/05/29 08:43
题意可以归纳为：求一条线段和雨滴的交的总长度。
分析：雨滴和线段的交点可以分为三角形和半圆的交点，注意线段可能会重复, 扫描线判重就可以了。
#include <iostream>#include <cstdio>#include <cmath>#include <algorithm>#include <string>#include <cstring>#include <vector>#define FOR(i, n) for(int i = 0; i < n; i++)#define MEM(array) memset(array, 0, sizeof(array))#define eps 1e-7#define INF 1e10#define PI acos(-1.0)using namespace std;inline int sgn(const double &x){return x > eps ? 1 : (x < -eps ? -1 : 0);}inline double sqr(const double &x){return x * x;}struct Point{        double x, y;        Point(){}        Point(const double &xx, const double &yy):x(xx), y(yy){}        Point operator + (const Point &a)const {            return Point(x + a.x, y + a.y);        }        Point operator - (const Point &a)const {            return Point(x - a.x, y - a.y);        }        Point operator * (const double &w)const{            return Point(x * w, y * w);        }        Point operator / (const double &w)const{            return Point(x / w, y / w);        }        friend Point operator * (const double &w, const Point &a){            return Point(a.x * w, a.y * w);        }        friend double det(const Point &a, const Point &b){            return a.x * b.y - a.y * b.x;        }        friend double dot(const Point &a, const Point &b){            return a.x * b.x + a.y * b.y;        }        friend double dist(const Point &a, const Point &b){            return (b - a).len();        }        double len()const{            return sqrt( dot(*this, *this));        }        Point norm()const{            double vLen = len();            return Point(x / vLen , y / vLen);        }        Point rotate(double angle){            double x1  = x * cos(angle) - y * sin(angle);            double y1  = x * sin(angle) + y * cos(angle);            return Point(x1, y1);        }        bool operator < (const Point &a)const {            return sgn(x - a.x) < 0 || (sgn(x  - a.x) == 0 && sgn(y - a.y) > 0);        }        bool operator > (const Point &a)const {            return sgn(x - a.x) > 0 || (sgn(x  - a.x) == 0 && sgn(y - a.y) < 0);        }        bool operator == (const Point &a)const {            return sgn(x - a.x) == 0 && sgn(y - a.y) == 0;        }        void in(){            scanf("%lf %lf", &x, &y);        }        void out()const{            printf("%.4f   %.4f\n", x, y);        }};struct Line{    Point s, t;    Line(){}    Line(const Point &ss, const Point &tt):s(ss), t(tt){}    friend bool lineParallelLine(const Line &l1, const Line &l2){        return sgn(det(l1.t - l1.s, l2.t - l2.s)) == 0;    }    friend bool isPointOnLine(const Point &a, const Line &line){        Point va = line.s - a, vb = line.t - a;        int res1 = sgn(det(va, vb));        if(res1 != 0)return false;        return sgn( dot(va, vb) ) <= 0;    }    friend double pointDistLine(const Point &p, const Line &line){        return fabs(det(p - line.s, line.t - line.s)/ (line.t- line.s).len());    }    friend Point pointProjLine(const Point &p, const Line &line){        return line.s + ( line.norm() * dot(p - line.s, line.t - line.s)/ (line.t - line.s).len() );    }    friend bool sameSide(const Line &line, const Point &a, const Point &b){        int res1 = sgn(det( a - line.s, line.t - line.s));        int res2 = sgn(det( b - line.s, line.t - line.s));        return res1 * res2 > 0;    }    friend vector<Point> lineInsectLine(const Line &l1, const Line &l2){        vector<Point>res;        if(lineParallelLine(l1, l2)){                if( sgn(pointDistLine(l1.s, l2))==0 )res.push_back(l1.s);                if( sgn(pointDistLine(l1.t, l2))==0 )res.push_back(l1.t);        }else {                Point vs = l1.s - l2.s, vl = l2.t - l2.s, vt = l1.t - l2.s;                double s1 = det(vs, vl), s2 = det(vt, vl);                res.push_back( (s1 * l1.t - s2 * l1.s)/(s1- s2));        }        return res;    }    Point norm()const{        return (t - s).norm();    }     Point vec()const{        return t - s;    }    void out()const{        s.out();        t.out();    }};int numl;struct Tri{    Point a[3];    Tri(){}    Tri(const Point &aa, const Point &bb, const Point &cc){        a[0] = aa; a[1] = bb; a[2] = cc;    }    friend vector<Point> triInsectLine(const Tri &tri, const Line &line){        vector<Point>res, tt;        for(int i = 0; i < 3; i++){            Line linet(tri.a[i], tri.a[(i + 1)%3]);            tt = lineInsectLine(line, linet);            FOR(j, tt.size()){                if(isPointOnLine(tt[j], linet))res.push_back(tt[j]);            }        }        sort(res.begin(), res.end());        int tn = unique(res.begin(), res.end()) - res.begin();        res.resize(tn);        return res;    }};struct Cir{    Point o;    double r;    Cir(){}    Cir(const Point &p, const double &rr):o(p), r(rr){}    friend vector<Point>  cirInsectLine(const Cir &cir, const Line &line){        vector<Point>res;        double dist = pointDistLine(cir.o, line);        if(dist < cir.r){            double len = sqrt(sqr(cir.r) - sqr(dist));            Point re = pointProjLine(cir.o, line);            Point tt1 = re - (line.norm() * len), tt2 = re + (line.norm() * len);            if( sgn(tt1.y - cir.o.y) < 0) res.push_back(tt1);            if( sgn(tt2.y - cir.o.y) < 0) res.push_back(tt2);        }        return res;    }    void in(){        o.in();        scanf("%lf",&r);    }};Point endPoint, srcPoint;Line mainLine, endLine;struct Rain{    Tri tri;    Cir cir;    Rain(){}    friend Line rainInsectLine(const Rain &rain, const Line &line){        vector <Point>res;        vector<Point>res1 = triInsectLine(rain.tri, line);        vector<Point>res2 = cirInsectLine(rain.cir, line);        Point leftPoint = line.t, rightPoint = line.s;        FOR(i, res1.size()){            res.push_back(res1[i]);        }        FOR(i, res2.size()){           res.push_back(res2[i]);        }        int len = res.size();        if(len > 1){            FOR(i, len){                if(leftPoint > res[i])leftPoint = res[i];                if(rightPoint < res[i])rightPoint = res[i];            }            if(leftPoint < line.s)leftPoint = line.s;            if(rightPoint > line.t)rightPoint = line.t;        }else {            leftPoint = rightPoint;        }        return Line(leftPoint, rightPoint);    }    void in(){        cir.in();        double h;        scanf("%lf", &h);        Point a(cir.o.x - cir.r, cir.o.y), b(cir.o.x + cir.r, cir.o.y), c(cir.o.x, cir.o.y + h);        tri = Tri(a, b, c);    }}rain[11111];double va, vb, vr,  t, x;int n;Point vMain;void init(){    srcPoint = Point(x, 0);    t += t *va/ (vb - va);    vMain = Point(-va, vr);    endPoint = srcPoint + vMain * t;    mainLine = Line(endPoint, srcPoint);}struct pointR{    Point p;    int type;    bool operator < (const pointR &a)const {        return p < a.p;    }}pr[11111];int ca = 0;double ans = 0;void solve(){    ans = 0;    FOR(i, n){        Line line = rainInsectLine(rain[i], mainLine);        pr[i * 2].p = line.s; pr[i * 2].type = 1;        pr[i * 2 + 1].p = line.t; pr[i * 2 + 1].type = -1;    }    int cnt = 0;    sort(pr, pr + 2 * n);    FOR(i, 2 * n){        if(cnt){            ans += fabs( Line(pr[i -1].p, pr[i].p).vec().len());        }        cnt += pr[i].type;    }    printf("Case %d: %.4f\n", ++ca, ans / vMain.len());}int main(){    int T;    scanf("%d", &T);    while(T--){        scanf("%lf %lf %lf %lf %lf", &va, &vb, &vr, &t, &x);        scanf("%d", &n);        FOR(i, n){            rain[i].in();        }        init();        solve();    }    return 0;}/*211 2 1 5 01-4 5 2 2*/