Submission #1196250

#	Time	Username	Problem	Language	Result	Execution time	Memory
1196250		cpismylifeOwO	Mobile (BOI12_mobile)	C++20	27 / 100	1097 ms	31680 KiB

mobile

#include <bits/stdc++.h>

using namespace std;

const long long mod = 1e9 + 7;
const int MaxN = 1e6 + 5;

int n;
long double l;
pair<long double, long double> arr[MaxN];

void Inp()
{
    cin >> n >> l;
    for (int x = 1; x <= n; x++)
    {
        cin >> arr[x].first >> arr[x].second;
    }
}

bool Check(long double k)
{
    vector<pair<long double, long double>> now;
    now.push_back(make_pair(0, l));
    for (int x = 1; x <= n; x++)
    {
        if (abs(arr[x].second) >= k)
        {
            continue;
        }
        long double p = sqrtl(k * k - arr[x].second * arr[x].second);
        vector<pair<long double, long double>> add;
        if (arr[x].first - p >= 0.0)
        {
            add.push_back(make_pair(0, min((long double)arr[x].first - p, l)));
        }
        if (arr[x].first + p <= l)
        {
            add.push_back(make_pair(max((long double)arr[x].first + p, (long double)0), l));
        }
        vector<pair<long double, long double>> tmp = now;
        now.clear();
        for (pair<long double, long double>& x : tmp)
        {
            for (pair<long double, long double>& y : add)
            {
                long double l = max(x.first, y.first), r = min(x.second, y.second);
                if (l <= r)
                {
                    now.push_back(make_pair(l, r));
                }
            }
        }
    }
    return !now.empty();
}

void Exc()
{
    long double l = 0, r = 2e9, mid, res = 0;
    while (r - l > 1e-3)
    {
        mid = (l + r) / 2.0;
        if (Check(mid))
        {
            res = mid;
            l = mid;
        }
        else
        {
            r = mid;
        }
    }
    cout << fixed << setprecision(3) << res;
}

int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    int test = 1;
    //cin >> test;
    for (int x = 1; x <= test; x++)
    {
        Inp();
        Exc();
    }
    return 0;
}

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