Submission #464133

#	Time	Username	Problem	Language	Result	Execution time	Memory
464133		dqk	Mobile (BOI12_mobile)	C++17	0 / 100	1099 ms	126340 KiB

mobile

#include <bits/stdc++.h>

int main() {
    std::ios_base::sync_with_stdio(false);
    std::cin.tie(nullptr);
    int n;
    long 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]);
    }
    long double d1 = sqrt(p[0][0] * p[0][0] + p[0][1] * p[0][1]);
    long double d2 = sqrt((p[0][0] - L) * (p[0][0] - L) + p[0][1] * p[0][1]);
    long double lo = 0, hi = std::max(d1, d2);
    while(hi - lo > 1e-4) {
        long double mi = (lo + hi) / 2;
        std::vector<std::vector<long double>> u;
        bool ltok = false;
        bool rtok = false;
        for (int i = 0; i < n; ++i) {
            long double h = p[i][1];
            if (h > mi)
                continue;
            long double lf = p[i][0] - sqrt(mi * mi - h * h);
            long double rt = p[i][0] + sqrt(mi * mi - h * h);
            if (rt < 0.0 || lf > L)
                continue;
            lf = (lf > 0.0 ? lf : 0.0);
            rt = std::min(rt, L);
            u.push_back({lf, rt});
            if (rt == L)
                rtok = true;
            if (lf == 0.0)
                ltok = true;
        }
        sort(u.begin(), u.end());
        bool ok = rtok & ltok;
        for (int i = 0; i < u.size() - 1 && ok; ++i) {
            if (u[i + 1][0] > u[i][1])
                ok = false;
        }
        if (ok) {
            hi = mi;
        }
        else {
            lo = mi;
        }
    }
    std::cout << lo << "\n";
    return 0;
}

Compilation message (stderr)

mobile.cpp: In function 'int main()':
mobile.cpp:40:27: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::vector<long double> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   40 |         for (int i = 0; i < u.size() - 1 && ok; ++i) {
      |                         ~~^~~~~~~~~~~~~~

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