CF793C Mice problem 题解

#pragma GCC optimize(3, "Ofast", "inline")
#include <bits/stdc++.h>
#define int long long
using namespace std;
const int N = 500010;
signed main() {
    cin.tie(0)->sync_with_stdio(false);
    cout << fixed << setprecision(15);
    int T;
    cin >> T;
    int x1, y1, x2, y2;
    cin >> x1 >> y1 >> x2 >> y2;
    vector<tuple<int, int, int>> v;
    while (T--) {
        int x_1, y_1, x_2, y_2;
        cin >> x_1 >> x_2 >> y_1 >> y_2;
        if (y_1) {
            v.emplace_back(x_1, y_1, 1);
        } else {
            if (x1 < x_1 && x_1 < x2) ;
            else {
                cout << "-1\n";
                return 0;
            }
        }
        if (y_2) {
            v.emplace_back(x_2, y_2, 0);
        } else {
            if (y1 < x_2 && x_2 < y2) ;
            else {
                cout << "-1\n";
                return 0;
            }
        }
    }
    double L = 0, R = 1e18;
    for (auto &[x, y, o] : v) {
        if (o) {
            double v1 = 1. * (x1 - x) / y;
            double v2 = 1. * (x2 - x) / y;
            if (v1 > v2) swap(v1, v2);
            L = max(L, v1), R = min(R, v2);
        } else {
            double v1 = 1. * (y1 - x) / y;
            double v2 = 1. * (y2 - x) / y;
            if (v1 > v2) swap(v1, v2);
            L = max(L, v1), R = min(R, v2);
        }
    }
    if (L < R) cout << L << '\n';
    else cout << -1 << '\n';
    return 0;
}