Submission #974383

#	Time	Username	Problem	Language	Result	Execution time	Memory
974383		vjudge1	Mobile (BOI12_mobile)	C++17	100 / 100	418 ms	27588 KiB

mobile

#include <bits/stdc++.h>
using i64 = long long;

int main() {
    std::ios::sync_with_stdio(false);
    std::cin.tie(nullptr);

    int N, L;
    std::cin >> N >> L;

    std::vector<std::pair<int, int>> p(N);
    for (auto &[x, y] : p) {
        std::cin >> x >> y;
    }

    auto check = [&](double r) {
        double cur = 0;
        for (auto [x, y] : p) {
            double d = std::sqrt(r * r - 1.0 * y * y);
            if (x - d <= cur) {
                cur = std::max(cur, x + d);
            }
        }
        return cur >= L;
    };

    double ans = [&]() {
        double l = 0, r = 3E9;
        while (r - l > 1E-5) {
            double x = l + (r - l) / 2;
            if (check(x)) {
                r = x;
            } else {
                l = x;
            }
        }
        return l;
    }();

    std::cout << std::fixed << std::setprecision(4) << ans << "\n";

    return 0;
}

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• Subtask 2: 4 / 4
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• Subtask 20: 5 / 5
• Subtask 21: 5 / 5