Submission #973346

#	Time	Username	Problem	Language	Result	Execution time	Memory
973346		IdanRosen	Mobile (BOI12_mobile)	C++98	50 / 100	1098 ms	91900 KiB

mobile

#include <bits/stdc++.h>

using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<ld, ld> pld;

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);

    ll n, l;
    cin >> n >> l;

    vector<pld> arr(n);
    for (auto &ref: arr) cin >> ref.first >> ref.second;

    ld start = 0;
    ld end = 1.42e9;
    while (end - start > 1e-6) {
        ld mid = (start + end) / 2;

        bool check = false;
        {
            vector<pld> ranges;
            for (int i = 0; i < n; i++) {
                if (mid < abs(arr[i].second)) continue;

                ld center = arr[i].first;
                ld delta = sqrt(mid * mid - (ld) (arr[i].second * arr[i].second));
                ranges.emplace_back(center - delta, center + delta);
            }

            std::sort(ranges.begin(), ranges.end(), [](const pld& left, const pld& right) -> bool {
                return left.first < right.first;
            });

            ld curr_len = 0;
            for (auto &range: ranges) {
                if (range.first <= curr_len) {
                    curr_len = max(curr_len, range.second);
                }
            }

           if (curr_len >= (ld) l)
               check = true;
           else
               check = false;

        }

        if (check)
            end = mid;
        else
            start = mid;
    }

    cout << fixed << setprecision(6) << start << endl;
}

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