Submission #1249029

#	Time	Username	Problem	Language	Result	Execution time	Memory
1249029		mirbek01	Mobile (BOI12_mobile)	C++20	100 / 100	688 ms	35832 KiB

mobile

#include <bits/stdc++.h>

using namespace std;

#define double long double

double dist(double x, double y, double a, double b) {
    return sqrt((x - a) * (x - a) + (y - b) * (y - b));
}

signed main() {
    int n;
    double L;
    cin >> n >> L;

    vector <double> x(n), y(n);
    for (int i = 0; i < n; i++) {
        cin >> x[i] >> y[i];
        y[i] = abs(y[i]);
    }

    auto get_point = [&](int i, int j) {
        return ((x[i] * x[i] + y[i] * y[i]) - (x[j] * x[j] + y[j] * y[j])) / (2.0 * (x[i] - x[j]));
    };  

    deque <int> stk;
    for (int i = 0; i < n; i++) {
        if (!stk.empty() && x[stk.back()] == x[i]) {
            if (y[i] >= y[stk.back()]) {
                continue;
            } 
            stk.pop_back();
        }
        while (stk.size() > 1 && get_point(stk.back(), i) < get_point(stk[stk.size() - 2], stk.back())) stk.pop_back();
        stk.push_back(i);
    }

    while (stk.size() > 1 && get_point(stk[0], stk[1]) < 0) {
        stk.pop_front();
    }
    while (stk.size() > 1 && get_point(stk[stk.size() - 2], stk[stk.size() - 1]) > L) {
        stk.pop_back();
    }

    double ans = 0;
    for (int i = 0; i < stk.size(); i++) {
        if (i) {
            if (get_point(stk[i - 1], stk[i]) < 0 || get_point(stk[i - 1], stk[i]) > L) continue;
            ans = max(ans, dist(x[stk[i]], y[stk[i]], get_point(stk[i - 1], stk[i]), 0));
        } else {
            ans = max(ans, dist(x[stk[i]], y[stk[i]], 0, 0));
        }
        if (i + 1 < stk.size()) {
            if (get_point(stk[i], stk[i + 1]) < 0 || get_point(stk[i], stk[i + 1]) > L) continue;
            ans = max(ans, dist(x[stk[i]], y[stk[i]], get_point(stk[i], stk[i + 1]), 0));
        } else {
            ans = max(ans, dist(x[stk[i]], y[stk[i]], L, 0));
        }
    }

    cout << fixed << setprecision(3) << ans << endl;
}

• Subtask 1: 4 / 4
• Subtask 2: 4 / 4
• Subtask 3: 4 / 4
• Subtask 4: 4 / 4
• Subtask 5: 4 / 4
• Subtask 6: 5 / 5
• Subtask 7: 5 / 5
• Subtask 8: 5 / 5
• Subtask 9: 5 / 5
• Subtask 10: 5 / 5
• Subtask 11: 5 / 5
• Subtask 12: 5 / 5
• Subtask 13: 5 / 5
• Subtask 14: 5 / 5
• Subtask 15: 5 / 5
• Subtask 16: 5 / 5
• Subtask 17: 5 / 5
• Subtask 18: 5 / 5
• Subtask 19: 5 / 5
• Subtask 20: 5 / 5
• Subtask 21: 5 / 5