Submission #1098015

#	Time	Username	Problem	Language	Result	Execution time	Memory
1098015		0x34c	Mobile (BOI12_mobile)	C++17	95 / 100	562 ms	131072 KiB

mobile

#include <bits/stdc++.h>
#define ll long long
#define pii pair<int, int>
#define endl '\n'
#define int ll
#define ld long double
#define pdd pair<ld, ld>

using namespace std;

int dist2(pii a, pii b)
{
    return (a.first - b.first) * (a.first - b.first) + (a.second - b.second) * (a.second - b.second);
}

ld dist(pii a, ld x)
{
    return sqrt((((ld)a.first) - x) * (((ld)a.first) - x) + (ld)(a.second * a.second));
}

const int INF2 = 1e12;
const int INF = 1e9 + 1;
ld eps = 1e-4;

signed main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);

    int N, L;
    cin >> N >> L;

    vector<pii> inp(N);
    map<int, int> closest;
    for (int i = 0; i < N; i++)
    {
        int x, y;
        cin >> x >> y;

        inp[i] = {x, y};

        if (!closest.count(x))
            closest[x] = y;
        else
            closest[x] = (abs(closest[x]) > abs(y) ? y : closest[x]);
    }

    vector<pii> pts;
    for (pii p : closest)
        pts.push_back(p);

    N = pts.size();

    auto calc_bp = [&](int idx1, int idx2)
    {
        ld x1 = pts[idx1].first, y1 = pts[idx1].second;
        ld x2 = pts[idx2].first, y2 = pts[idx2].second;

        return ((ld)0.5) * (x1 + x2 + (y1 * y1 - y2 * y2) / (x1 - x2));
    };

    stack<int> stk;
    stk.push(0);
    vector<ld> dists, bps;
    for (int i = 1; i < N; i++)
    {
        while (stk.empty())
        {
        }
        ld bp = calc_bp(stk.top(), i);
        bool emp = false;

        while (!bps.empty() && bps.back() > bp)
        {
            bps.pop_back();
            stk.pop();
            dists.pop_back();
            if (stk.empty())
                emp = true;
            else
                bp = calc_bp(stk.top(), i);
        }

        if (!emp)
        {
            bps.push_back(bp);
            dists.push_back(dist(pts[i], bp));
        }
        stk.push(i);
    }

    ld mx_dist = 0;
    for (int i = 0; i < (bps.empty() ? 0 : bps.size()); i++)
    {
        if (bps[i] < 0 || bps[i] > L)
            continue;
        mx_dist = max(mx_dist, dists[i]);
    }

    ld mn_start = INF2, mn_end = INF2;
    for (int i = 0; i < N; i++)
    {
        mn_start = min(mn_start, dist(pts[i], 0));
        mn_end = min(mn_end, dist(pts[i], L));
    }

    mx_dist = max({mx_dist, mn_start, mn_end});
    cout << setprecision(4) << fixed << mx_dist << endl;
}

Compilation message (stderr)

mobile.cpp: In function 'int main()':
mobile.cpp:93:23: warning: comparison of integer expressions of different signedness: 'long long int' and 'long unsigned int' [-Wsign-compare]
   93 |     for (int i = 0; i < (bps.empty() ? 0 : bps.size()); i++)
      |                     ~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 4 / 4
• Subtask 2: 4 / 4
• Subtask 3: 4 / 4
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• Subtask 21: 5 / 5