Submission #698066

#	Time	Username	Problem	Language	Result	Execution time	Memory
698066		caganyanmaz	Mobile (BOI12_mobile)	C++14	8 / 100	1100 ms	78568 KiB

mobile

#include <bits/stdc++.h>
#define int int64_t
#define f first
#define s second
#define mp make_pair
using namespace std;

bool check(double r, int L, const vector<array<int, 2>>& stations)
{
    set<pair<double, double>> intervals;
    for (const array<int, 2>& station : stations)
    {
        double diff_sqrd = r * r - station[1] * station[1];
        if (diff_sqrd < 0)
            continue;
        double diff = sqrt(diff_sqrd);
        double _l = station[0] - diff, _r = station[0] + diff;
        if (_l > L || _r < 0)
            continue;
        intervals.insert(mp(_l, _r));
    }
    if (intervals.begin()->f > 0)
        return false;
    double last = (*intervals.begin()).s;
    for (auto it = intervals.begin(); it != intervals.end() && last < L && it->f <= last; it++)
    {
        last = max(last, it->s);
    }
    return last >= L;
}

constexpr static int PRECISION = 1e5;

int32_t main()
{
    
    int N, L;
    cin >> N >> L;
    vector<array<int, 2>> stations(N);
    for (int i = 0; i < N; i++)
        for (int j = 0; j < 2; j++)
            cin >> stations[i][j];
    double l = 0, r = 4e9;
    while (r - l > 0.001)
    {
        double m = (r+l)*0.5;
        if (check(m, L, stations))
            r = m;
        else
            l = m;
    }
    cout << r << "\n";
}

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