Submission #1294373

#	Time	Username	Problem	Language	Result	Execution time	Memory
1294373		srittheboss	Mobile (BOI12_mobile)	C++20	4 / 100	1098 ms	63820 KiB

mobile

#include "bits/stdc++.h"
#define INF 1e18
using namespace std;

bool test(int n, int l, double r, vector<pair<double, double>> stations) {
    vector<pair<double, double>> intervals;

    for (int i = 0; i < n; i++) {
        if (stations[i].second >= -r && stations[i].second <= r) {
            double x = stations[i].first;
            double y = stations[i].second;
            double lower = x - pow(pow(r, 2) - pow(y, 2), 0.5);
            double upper = x + pow(pow(r, 2) - pow(y, 2), 0.5);
            intervals.push_back({lower, upper});
        }
    }

    stack<pair<double, double>> s;

    for (auto interval : intervals) {
        while (!s.empty() && s.top().second >= interval.first) {
            interval = {min(interval.first, s.top().first), max(interval.second, s.top().second)};
            s.pop();
        }
        s.push(interval);
    }

    if (s.size() == 1 && s.top().first <= 0 && s.top().second >= l) {
        return true;
    }

    return false;

}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(NULL);

    int n, l;
    cin >> n >> l;
    vector<pair<double, double>> stations(n);

    for (int i = 0; i < n; i++) {
        cin >> stations[i].first >> stations[i].second;
    }


    long long lo = 0, hi = 1e12;

    while (lo < hi) {
        long long mid = lo + (hi - lo) / 2;
        if (test(n, l, ((double) mid) / 10000, stations)) {
            hi = mid;
        } else {
            lo = mid + 1;
        }
    }

    cout << ((double) lo) / 10000 << endl;


}

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