nyoj 665桌球碰撞

比赛时想着要模拟过程，没法下手，做后没作出开，原来是把速度v分解到x，y方向上。

在一个周期内求解。

#include<cstdio>
#include<iostream>
#include<cstring>
#include<cmath>
using namespace std;
const double PI=acos(-1); //刚开时自己定义的，有误差，偶然发现这个无错。此值为3.141593
const double eps=1e-6;
double fun1(double x,double vx,double s,double r,double l)
{
    double c=2*(l-2*r);
    if(vx==0) return x;
    double t1=c/vx;
    while(s-t1>=0+eps) s-=t1;
    double len,tt;
    if(s==0+eps) x=x;
    else
    {
        len=l-r-x;
        tt=len/vx;
        if(s-tt<=eps) x=x+vx*s;
        else
        {
            s=s-tt;
            len=l-2*r;
            tt=len/vx;
            if(s-tt<=eps) x=l-r-vx*s;
            else
            {
                s-=tt;
                len=x-r;
                tt=len/vx;
                if(s-tt<=eps) x=r+vx*s;
            }
        }
    }
    return x;
}
double fun2(double x,double vx,double s,double r,double l)
{
    if(vx==0) return x;
    double c=2*(l-2*r);
    double tt=c/vx;
    while(s-tt>=0+eps) s-=tt;
    double len;
    if(s==0+eps) x=x;
    else
    {
        len=x-r;
        tt=len/vx;
        if(s-tt<=eps) x=x-vx*s;
        else
        {
            s=s-tt;
            len=l-2*r;
            tt=len/vx;
            if(s-tt<=eps) x=r+vx*s;
            else
            {
                s-=tt;
                len=l-r-x;
                tt=len/vx;
                if(s-tt<=eps) x=l-r-vx*s;
            }
        }
    }
    return x;
}
int main()
{
    //freopen("Input.txt","r",stdin);
    double l,w,x,y,r,a,v,s;
    while(~scanf("%lf%lf%lf%lf%lf%lf%lf%lf",&l,&w,&x,&y,&r,&a,&v,&s))
    {
        if(l<=0) break;
        double a1=(a/180)*PI;
        double vx=v*cos(a1);
        double vy=v*sin(a1);
        double xx,yy;
        if(a>=0&&a<=90)
        {
            xx=fun1(x,vx,s,r,l);
            yy=fun1(y,vy,s,r,w);
        }
        else if(a>90&&a<=180)
        {
            vx=vx<0?-vx:vx; vy=vy<0?-vy:vy;
            yy=fun1(y,vy,s,r,w);
            xx=fun2(x,vx,s,r,l);
        }
        else if(a>180&&a<=270)
        {
            vx=vx<0?-vx:vx; vy=vy<0?-vy:vy;
            xx=fun2(x,vx,s,r,l);
            yy=fun2(y,vy,s,r,w);
        }
        else
        {
            vx=vx<0?-vx:vx; vy=vy<0?-vy:vy;
            xx=fun1(x,vx,s,r,l);
            yy=fun2(y,vy,s,r,w);
        }
        printf("%.2lf %.2lf\n",xx,yy);
    }
    return 0;
}