제출 #990607

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
990607		Ska	Mobile (BOI12_mobile)	C++14	50 / 100	1074 ms	63508 KiB

mobile

#include <bits/stdc++.h>
using namespace std;
 
const int N = 1e6 + 5;
 
int n;
double m;
double x[N], y[N];
 
pair<double, double> calc(double r, int i) {
    if (r < abs(y[i])) {
        return {-1, -1};
    }
    return {x[i] - sqrt(r * r - y[i] * y[i]), x[i] + sqrtl(r * r - y[i] * y[i])};
}
 
int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cin >> n >> m;
    double l = 2e9, r = 1.5e9;
    for (int i = 1; i <= n; ++i) {
        cin >> x[i] >> y[i];
        l = min(l, abs(y[i]));
    }
    while (r - l >= 1e-3) {
        vector<pair<double, double>> segments;
        double mid = (l + r) / 2;
        for (int i = 1; i <= n; ++i) {
            auto x = calc(mid, i);
            if (x.first != -1 || x.second != -1) {
                segments.emplace_back(x.first, x.second);
            }
        }
        sort(segments.begin(), segments.end());
        double bound = 0;
        for (auto x : segments) {
            if (x.first > bound) {
                break;
            }
            bound = max(bound, x.second);
            if (bound >= m) {
                break;
            }
        }
        if (bound >= m) {
            r = mid;
        } else {
            l = mid;
        }
    }
    cout << fixed << setprecision(6) << l << '\n';
}

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