Submission #464172

#	Time	Username	Problem	Language	Result	Execution time	Memory
464172		dqk	Mobile (BOI12_mobile)	C++17	4 / 100	592 ms	55084 KiB

mobile

#include <bits/stdc++.h>

int main() {
    std::ios_base::sync_with_stdio(false);
    std::cin.tie(nullptr);
    int n;
    double L;
    std::cin >> n >> L;
    std::vector<std::vector<int>> p(n, std::vector<int>(2, 0));
    for (int i = 0; i < n; ++i) {
        std::cin >> p[i][0] >> p[i][1];
        p[i][1] = abs(p[i][1]);
    }
    sort(p.begin(), p.end());
    double lo = 0.0, hi = 4e9;
    while(hi - lo > 1e-3) {
        double mi = (lo + hi) / 2;
        double cur = 0.0;
        for (int i = 0; i < n; ++i) {
            double h = p[i][1];
            if (h > mi)
                continue;
            double d = sqrt(mi * mi - h * h);
            if (cur >= p[i][0] - d)
                cur = std::max(cur, p[i][0] + d);
        }
        bool ok = cur >= L;
        if (ok) {
            hi = mi;
        }
        else {
            lo = mi;
        }
    }
    std::cout << lo << "\n";
    return 0;
}

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