【优秀题解】1175：台球碰撞

#include <stdio.h>
#include <math.h>
int    n = 0;
double    X1, Y1, x, y, R;
void endpoint( double L, double W ); /* x,y is start point  X1,Y1 is end point */
int main()
{
    double L, W, a, v, s;
    scanf( "%lf%lf%lf%lf%lf%lf%lf%lf", &L, &W, &x, &y, &R, &a, &v, &s );
    while ( L != 0 && W != 0 && x != 0 && y != 0 && R != 0 && a != 0 && v != 0 && s != 0 )
    {
        a    = a * asin( 1 ) * 2 / 180;
        X1    = x + s*v*cos( a );
        Y1 = y + s*v*sin( a );
        while ( X1<0 || X1>L || Y1<0 || Y1>W )
        {
            endpoint( L - R, W - R );
        }
        if ( X1 >= 0 + R && X1 <= L && Y1 >= 0 + R && Y1 <= W )
        {
            printf( "%.2lf %.2lf\n", X1, Y1 );
        }
        scanf( "%lf%lf%lf%lf%lf%lf%lf%lf", &L, &W, &x, &y, &R, &a, &v, &s );
    }
/*for(int i=0;i<n;i++)
 * {
 * printf("%.2lf %.2lf\n",xx[i],yy[i]);
 *
 * }*/
    return(0);
}
void endpoint( double L, double W )
{
    double upx, downx, righty, lefty, slope;
    slope = (Y1 - y) / (X1 - x);
    upx    = (W - y) / slope + x;
    downx    = (0.0 + R - y) / slope + x;
    righty    = slope * (L - x) + y;
    lefty    = slope * (0.0 + R - x) + y;
    if ( Y1 > W && y < W && upx >= 0 + R && upx <= L )
    {
        x    = upx;
        y    = W;
        Y1 = Y1 - 2 * (Y1 - W);
        return;
    }  /* yu shangbianjie xiang jiao */
    else
    if ( Y1 < 0 + R && y > 0 + R && downx >= 0 + R && downx <= L )
    {
        x    = downx;
        y    = 0 + R;
        Y1 = Y1 - 2 * (Y1 - R);
        return;
    } /* yu xiabianjie */
    else
    if ( X1 > L && x < L && righty >= 0 + R && righty <= W )
    {
        x    = L;
        y    = righty;
        X1 = X1 - 2 * (X1 - L);
        return;
    } /* YU YOU BIANJIE */
    else
    if ( X1 < 0 + R && x > 0 + R && lefty >= 0 + R && lefty <= W )
    {
        x    = 0 + R;
        y    = lefty;
        X1 = X1 - 2 * (X1 - R);
        return;
    }
    return;
}