好神的几何题 把一个点不动作为参照物 然后就变成了只有一个点在动 画出来就是这样
然后就是求 一个点到两组平行线段的距离最小值
#include<cstdio> #include<cstdlib> #include<algorithm> #include<cmath> using namespace std; typedef double ld; inline ld sqr(ld x){ return x*x; } inline int sgn(ld x){ if (fabs(x)<1e-8) return 0; return x<0?-1:1; } struct PP{ ld x,y; PP(ld x=0,ld y=0):x(x),y(y) { } bool read() { double _x,_y; if (scanf("%lf%lf",&_x,&_y)==-1) return 0; x=_x; y=_y; return 1; } ld dist() { return sqrt(x*x+y*y); } PP operator - () { return PP(-x,-y); } friend PP operator + (PP A,PP B) { return PP(A.x+B.x,A.y+B.y); } friend PP operator - (PP A,PP B) { return PP(A.x-B.x,A.y-B.y); } friend PP operator * (PP A,ld B) { return PP(A.x*B,A.y*B); } friend PP operator / (PP A,ld B) { return PP(A.x/B,A.y/B); } friend ld operator * (PP A,PP B) { return A.x*B.x+A.y*B.y; } friend ld cross(PP A,PP B) { return A.x*B.y-A.y*B.x; } friend ld dist(PP A,PP B) { return sqrt(sqr(A.x-B.x)+sqr(A.y-B.y)); } }; inline ld calc(PP p,PP A,PP B){ if (sgn(A.x-B.x)==0 && sgn(A.y-B.y)==0) return dist(p,A); if (sgn((p-A)*(B-A))>0 && sgn((p-B)*(A-B))>0) return fabs(cross(p-A,B-A))/dist(A,B); return min(dist(A,p),dist(B,p)); } inline ld calc(PP p,PP A,PP B,PP D){ int L=0,R=1<<28,m1,m2; ld f1,f2; while (R-L>12){ m1=(L+L+R)/3; m2=(L+R+R)/3; f1=calc(p,A+D*m1,B+D*m1); f2=calc(p,A+D*m2,B+D*m2); if (f1<f2) R=m2; else L=m1; } ld ret=1e20; for (int i=L;i<=R;i++) ret=min(ret,calc(p,A+D*i,B+D*i)); return ret; } ld vw,vt; PP w0,w1,t0,t1; ld mind,maxd; inline void Solve(){ ld Time=dist(t0,t1)/vt; PP tg=(t1-t0)/dist(t0,t1)*vt; PP wg=(w1-w0)/dist(w0,w1)*vw; PP p1=t0+(tg-wg)*Time; PP p2=p1+(-tg-wg)*Time; ld d1=calc(w0,t0,p1,p2-t0); ld d2=calc(w0,p1,p2,p2-t0); ld d=min(d1,d2); if (sgn(d-maxd)>0) printf("Miss\n"); else if (sgn(mind-d)>0) printf("Dangerous\n"); else printf("Perfect\n"); } int main(){ freopen("t.in","r",stdin); freopen("t.out","w",stdout); while (w0.read()){ w1.read(); scanf("%lf",&vw); t0.read(); t1.read(); scanf("%lf",&vt); scanf("%lf%lf",&mind,&maxd); Solve(); } return 0; }