BZOJ1857: [Scoi2010]传送带(三分套三分)

#include<cstdio>
#include<cmath>
#include<algorithm>
#define eps 1e-3
using namespace std;
inline int read() {
    char c = getchar(); int x = 0, f = 1;
    while(c < '0' || c > '9') {if(c == '-') f = -1; c = getchar();}
    while(c >= '0' && c <= '9') x = x * 10 + c - '0',c = getchar();
    return x * f;
}
int Ax, Ay, Bx, By, Cx, Cy, Dx, Dy, P, Q, R;
double dis(double x, double y, double x2, double y2) {
    return sqrt((x2 - x) * (x2 -x) + (y2 - y) * (y2 - y));
}
double check2(double x,double y,double x2,double y2) {
    return dis(Ax, Ay, x, y) / P + dis(x, y, x2, y2) / R + dis(x2, y2, Dx, Dy) / Q;
}
double check(double x, double y) {
    double lx = Cx, ly = Cy, rx = Dx, ry = Dy, a, b;
    while(abs(rx - lx) > eps || abs(ry - ly) > eps) {
        double wx1 = (lx * 2 + rx) / 3, wy1 = (ly * 2 + ry) / 3,
               wx2 = (lx + rx * 2) / 3, wy2 = (ly + ry * 2) / 3;
        a = check2(x, y, wx1, wy1);
        b = check2(x, y, wx2, wy2);
        if(a > b) lx = wx1, ly = wy1;
        else rx = wx2, ry = wy2;
    }
    return check2(x, y, lx, ly); 
}
int main() {
    #ifdef WIN32
    freopen("a.in","r",stdin);
    #endif
    Ax = read(), Ay = read(), Bx = read(), By = read(), Cx = read(), Cy = read(), Dx = read(), Dy = read(), P = read(), Q = read(), R = read();
    double lx = Ax, ly = Ay, rx = Bx, ry = By;
    while(abs(rx - lx) > eps || abs(ry - ly) > eps) {
        double wx1 = (lx * 2 + rx) / 3, wy1 = (ly * 2 + ry) / 3,
               wx2 = (lx + rx * 2) / 3, wy2 = (ly + ry * 2) / 3;
        if(check(wx1, wy1) > check(wx2, wy2)) lx = wx1, ly = wy1;
        else rx = wx2, ry = wy2;
    }
    printf("%.2lf", check(lx, ly));
    return 0;
}