Submission #1197702

#	Time	Username	Problem	Language	Result	Execution time	Memory
1197702		cpismylifeOwO	Mobile (BOI12_mobile)	C++20	25 / 100	1098 ms	31876 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;
    }
    sort(arr + 1, arr + n + 1);
}

stack<pair<long double, long double>> st;

bool Check(long double k)
{
    while (!st.empty())
    {
        st.pop();
    }
    for (int x = 1; x <= n; x++)
    {
        if (arr[x].second > k)
        {
            continue;
        }
        long double p = sqrt(k * k - arr[x].second * arr[x].second), l = arr[x].first - p, r = arr[x].first + p;
        while (!st.empty() && max(l, st.top().first) <= min(r, st.top().second))
        {
            l = min(l, st.top().first);
            r = max(r, st.top().second);
            st.pop();
        }
        st.push(make_pair(l, r));
    }
    while (!st.empty())
    {
        if (st.top().first <= 0 && l <= st.top().second)
        {
            return true;
        }
        st.pop();
    }
    return false;
}

void Exc()
{
    long double l = 0, r = 1e10, mid, res = 0;
    while (r - l > 1e-3)
    {
        mid = (l + r) / 2.0;
        if (Check(mid))
        {
            res = mid;
            r = mid;
        }
        else
        {
            l = 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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