Submission #1098024

#	Time	Username	Problem	Language	Result	Execution time	Memory
1098024		0x34c	Mobile (BOI12_mobile)	C++17	100 / 100	546 ms	114728 KiB

mobile

#include <bits/stdc++.h>
#define ll long long
#define pii pair<int, int>
#define endl '\n'
#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)
{
    ld x1 = a.first, y = a.second;
    return sqrt((x1 - x) * (x1 - x) + y * y);
}

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)
    {
        try
        {
            ld x1 = pts[idx1].first, y1 = pts[idx1].second;
            ld x2 = pts[idx2].first, y2 = pts[idx2].second;

            if (x1 - x2 == 0)
                return (ld)-1;
            return ((ld)0.5) * (x1 + x2 + (y1 * y1 - y2 * y2) / (x1 - x2));
        }
        catch (const std::exception &e)
        {
            return (ld)-1;
        }
    };

    stack<int> stk;
    stk.push(0);
    vector<ld> dists, bps;
    for (int i = 1; i < N; i++)
    {
        try
        {
            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);
        }
        catch (const std::exception &e)
        {
        }
    }

    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], (ld)0));
        mn_end = min(mn_end, dist(pts[i], (ld)L));
    }

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

Compilation message (stderr)

mobile.cpp:21:18: warning: overflow in conversion from 'double' to 'int' changes value from '1.0e+12' to '2147483647' [-Woverflow]
   21 | const int INF2 = 1e12;
      |                  ^~~~
mobile.cpp: In function 'int main()':
mobile.cpp:105:23: warning: comparison of integer expressions of different signedness: 'int' and 'long unsigned int' [-Wsign-compare]
  105 |     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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