"Half-Plane" bzoj1038 [ZJOI2008] Lookout tower

http://m.blog.csdn.net/blog/qpswwww/44105605

#include <cstdio> #include <cmath> #include <algorithm>using namespace std; #define EPS 0.0000001# Define N 311typedef Double db;const db Pi=acos ( -1.0); struct point{db x, y;}; typedef point Vector; Vector operator-(const point &a,const point &b) {return (Vector) {a.x-b.x,a.y-b.y};} Vector operator * (const vector &AMP;A,CONST db &k) {return (Vector) {a.x*k,a.y*k};} Vector operator + (const vector &a,const vector &b) {return (vector) {a.x+b.x,a.y+b.y};} DB Cross (Vector A,vector b) {return a.x*b.y-a.y*b.x;} struct line{point P; Vector v;    DB ang;        Line () {} line (const point &a,const point &b) {v=b-a;        P=a;        Ang=atan2 (v.y,v.x);       if (ang<0) Ang+=2.0*pi; }};bool operator < (const line &a,const line &b) {return a.ang<b.ang;} BOOL Onleft (line L,point a) {return cross (L.V,A-L.P) >0; Point Getjiaodian (line A,line b) {return a.p+a.v* (Cross (B.V,A.P-B.P)/cross (A.V,B.V)); int n; Point Ps[n]; Line Q[n];int Head=1,tail= 1;    Line Ls[n];void BPMJ () {sort (ls+1,ls+n+1);    Q[1]=LS[1]; for (int i=2;i<=n;++i) {while (head<tail&& (!        Onleft (Ls[i],ps[tail-1]))--tail; while (head<tail&& (!        Onleft (Ls[i],ps[head])) ++head;        Q[++tail]=ls[i];            if (Fabs (Q[TAIL].V,Q[TAIL-1].V)) <eps) {--tail;          if (Onleft (Q[TAIL],LS[I].P)) q[tail]=ls[i];      } if (Head<tail) Ps[tail-1]=getjiaodian (Q[tail-1],q[tail]); } while (head<tail&& (!    Onleft (Q[head],ps[tail-1]))--tail; Ps[tail]=getjiaodian (Q[tail],q[head]);} int nn;    Point A[n];d b ans=999999999999999999.0; #define INF 10000000000.0int Main () {//Freopen ("Bzoj1038.in", "R", stdin);    scanf ("%d", &nn);    for (int i=1;i<=nn;++i) scanf ("%lf", &a[i].x);    for (int i=1;i<=nn;++i) scanf ("%lf", &a[i].y);    for (int i=1;i<nn;++i) ls[++n]=line (a[i],a[i+1]);    Ls[++n]=line (point) {Inf,inf}, (point) {-inf,inf}); Ls[++n]=line ((Point) {-inf,inf}, (point) {-inf,-inf});    Ls[++n]=line (point) {-inf,-inf}, (point) {inf,-inf});    Ls[++n]=line (point) {Inf,-inf}, (point) {inf,inf});    BPMJ ();          for (int i=head;i<=tail;++i) for (int j=1;j<nn;++j) if (ps[i].x>=a[j].x&&ps[i].x<=a[j+1].x)            {db ty=a[j].y+ (ps[i].x-a[j].x)/(a[j+1].x-a[j].x) * (A[J+1].Y-A[J].Y);            Ans=min (Ans,ps[i].y-ty);          Break } for (int i=1;i<=nn;++i) {for (int j=head;j<tail;++j) if (a[i].x>=ps[j].x&&a[i].x&              lt;=ps[j+1].x) {db ty=ps[j].y+ (a[i].x-ps[j].x)/(ps[j+1].x-ps[j].x) * (PS[J+1].Y-PS[J].Y);            Ans=min (ANS,TY-A[I].Y); } if (a[i].x>=ps[tail].x&&a[i].x<=ps[head].x) {db ty=ps[tail].y+ (A[i].x-ps[tail].            x)/(ps[head].x-ps[tail].x) * (PS[HEAD].Y-PS[TAIL].Y);          Ans=min (ANS,TY-A[I].Y);    }} printf ("%.3lf\n", ans); return 0;}

Half-plane bzoj1038 [ZJOI2008] Lookout tower