Submission #550703

#	Time	Username	Problem	Language	Result	Execution time	Memory
550703		FromDihPout	Mobile (BOI12_mobile)	C++17	36 / 100	1101 ms	62992 KiB

mobile

/**
 *    author:  FromDihPout
 *    created: 2022-04-18
**/
 
#include <bits/stdc++.h>
using namespace std;

const double EPSILON = 1e-5;

int main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0);

    int n, l;
    cin >> n >> l;
    vector<array<double, 2>> p(n);
    for (int i = 0; i < n; i++) {
        cin >> p[i][0] >> p[i][1];
    }

    auto check = [&](double r) {
        vector<pair<double, double>> intervals(n);
        for (int i = 0; i < n; i++) {
            if (p[i][1] >= r) continue;
            double length = sqrt((r * r) - (p[i][1] * p[i][1]));
            intervals.emplace_back(p[i][0] - length, p[i][0] + length);
        }
        sort(intervals.begin(), intervals.end());

        double end = 0.0;
        for (auto [left, right] : intervals) {
            if (left > end) {
                return false;
            }
            end = max(end, right);
        }
        return end >= l;
    };

    double lo = 0, hi = 1e10;
    while (hi - lo > EPSILON) {
        double mid = (lo + hi) / 2;
        if (check(mid)) {
            hi = mid;
        } else {
            lo = mid;
        }
    }
    cout << fixed << setprecision(5) << lo << '\n';
    return 0;
}

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