Submission #781085

#	Time	Username	Problem	Language	Result	Execution time	Memory
781085		uped	Mobile (BOI12_mobile)	C++14	0 / 100	1083 ms	70748 KiB

mobile

#include<bits/stdc++.h>

using namespace std;

using ll = long long;

void fastio() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
}

int main() {
    fastio();
    int n, len;
    cin >> n >> len;
    vector<pair<int, int>> v(n);
    for (int i = 0; i < n; ++i) {
        int a, b;
        cin >> a >> b;
        v[i] = {a, b};
    }
    double l = 0.0, r = 1e12; // todo r
    for (int i = 0; i < 100; ++i) {
        double radius = (l + r) / 2.0;
        map<double, int> m;
        for (int j = 0; j < n; ++j) {
            int x = v[j].first;
            int y= v[j].second;
            double a = sqrt( radius * radius - y * y);
            if (x + a >= 0 && x - a <= len) {
                if (x + a <= len) {
                    --m[x + a + 1e-7];
                }
                ++m[max(x - a, 0.0)];
            }
        }
        int cur = 0;
        bool ok = true;
        for (auto& it : m) {
            cur += it.second;
            if (cur <= 0) {
                ok = false;
                break;
            }
        }
        if (ok) {
            r = radius;
        } else {
            l = radius;
        }
    }
    cout << setprecision(20) << r;
    return 0;
}

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