题解

#include <bits/stdc++.h>
int main() {
int n;
stdcin >> n;
stdvector<stdarray<int, 4>> rects(n);
for (auto &v : rects)
for (int &x : v)
stdcin >> x;

int xs, ys, xt, yt, ex = 0;
double v;
std::cin >> xs >> ys >> xt >> yt >> v;
if (xs == xt)
    return printf("%.8lf\n", std::abs(ys - yt) / v), 0;
if (xs > xt)
    std::swap(xs, xt), std::swap(ys, yt);

std::vector<int> x, y, tp;
auto add = [&](int _x, int _y, int _tp) { x.emplace_back(_x), y.emplace_back(_y), tp.emplace_back(_tp); };
add(xs, ys, 0);
for (int i = 1; i < n; i++) {
    if (rects[i][0] <= xs) {
        if (rects[i][0] == xs) { 
            if (ys > rects[i][3])
                ex += ys - rects[i][3], y[0] = rects[i][3];
            if (ys < rects[i][1])
                ex += rects[i][1] - ys, y[0] = rects[i][1];
        }
        continue;
    }
    if (rects[i][0] >= xt) {
        if (rects[i][0] == xt) {
            if (yt > rects[i - 1][3])
                ex += yt - rects[i - 1][3], yt = rects[i - 1][3];
            if (yt < rects[i - 1][1])
                ex += rects[i - 1][1] - yt, yt = rects[i - 1][1];
        }
        break;
    }
    add(rects[i][0], std::min(rects[i - 1][3], rects[i][3]), 1);
    add(rects[i][0], std::max(rects[i - 1][1], rects[i][1]), 2);
}
add(xt, yt, 1);

int m = x.size();
std::vector<double> f(m, 1e9);
f[0] = 0;
for (int i = 1; i < m; i++) {
    double lower = -1e9, upper = 1e9;
    for (int j = i - tp[i]; j >= 0; j--) {
        double k = (double)(y[i] - y[j]) / (x[i] - x[j]);
        if (lower <= k && k <= upper)
            f[i] = std::min(f[i], f[j] + hypot(x[i] - x[j], y[i] - y[j]));
        if (tp[j] == 1 && k > lower)
            lower = k; 
        if (tp[j] == 2 && k < upper)
            upper = k;
        if (lower > upper)
            break; 
    }
}

printf("%.8lf\n", (f.back() + ex) / v);
return 0;

}