Submission #944892

#	Time	Username	Problem	Language	Result	Execution time	Memory
944892		tmarcinkevicius	Event Hopping (BOI22_events)	C++14	10 / 100	1572 ms	415468 KiB

events

#include <bits/stdc++.h>
using namespace std;

#define int int64_t
typedef pair<int,int> pii;
typedef vector<int> vii;
#define MP make_pair
#define PB push_back
#define f first
#define s second
#define INF 2e18
#define fast_io() ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0)
#define all(x) (x).begin(), (x).end()
#define sz(x) ((ll)(x).size())



struct Interval
{
    int id;
    pii range;
};

int N, Q;
vector<Interval> intervals;
vector<pii> queries;

vector<vector<Interval>> adjSorted;
vector<set<int>> adjAll;

int32_t main()
{
    //fast_io();

    cin >> N >> Q;
    intervals = vector<Interval>(N + 1);
    adjAll = vector<set<int>>(N + 1);
    adjSorted = vector<vector<Interval>>(N + 1);

    //vector<pii> endPoints;
    // { time, 0 for start / 1 for end }

    for (int i = 1; i <= N; i++)
    {
        Interval inter;
        cin >> inter.range.f >> inter.range.s;

        inter.id = i;
        intervals[i] = inter;

        //endPoints.push_back({inter.range.f, 0});
        //endPoints.push_back({inter.range.s, 1});
    }

    queries = vector<pii>(Q);
    for (int i = 0; i < Q; i++)
    {
        cin >> queries[i].f >> queries[i].s;
    }

    //sort(all(endPoints));



    //sort(all(intervals), [](Interval a, Interval b)
    //    { return a.range.s < b.range.s; });

    for (int i = 1; i <= N; i++)
    {
        for (int j = 1; j <= N; j++)
        {
            if (i == j)
                continue;

            if (intervals[i].range.s >= intervals[j].range.f &&
                intervals[i].range.s <= intervals[j].range.s)
            {
                adjAll[i].insert(j);
            }
        }
    }


    for (int i = 1; i <= N; i++)
    {
        int bestE = -1;
        int bestId = -1;

        //cout << "adjAll[" << i << "]: {";
        for (int j : adjAll[i])
        {
            //cout << j << " ";
            adjSorted[i].push_back(intervals[j]);
        }
        //cout << "}\n";

        sort(all(adjSorted[i]), [](Interval a, Interval b)
            { return a.range.s < b.range.s; });
    }


    if (N * Q < (int)1e7)
    {
        for (int q = 0; q < Q; q++)
        {
            if (queries[q].f == queries[q].s)
            {
                cout << 0 << '\n';
                continue;
            }
            vector<int> dis(N + 1, INF);
            queue<int> qu;
            qu.push(queries[q].f);
            dis[queries[q].f] = 0;
            bool impossible = true;

            while (!qu.empty())
            {
                int fr = qu.front();
                qu.pop();
                // cout << "at: " << fr << '\n';

                if (adjAll[fr].count(queries[q].s))
                {
                    // cout << "can go already\n";
                    cout << dis[fr] + 1 << '\n';
                    impossible = false;
                    break;
                }

                if (adjSorted[fr].size() == 0)
                {
                    continue;
                }

                int low = 0;
                int high = adjSorted[fr].size() - 1;

                while (low < high)
                {
                    // cout << "(" << low << " " << high << ")\n";
                    int mid = low + (high - low + 1) / 2;

                    if (adjSorted[fr][mid].range.s <= intervals[queries[q].s].range.s)
                    {
                        low = mid;
                    }
                    else
                    {
                        high = mid - 1;
                    }
                }

                Interval bestNode = adjSorted[fr][low];

                if (bestNode.range.s <= intervals[queries[q].s].range.s &&
                    dis[bestNode.id] == INF)
                {
                    dis[bestNode.id] = dis[fr] + 1;
                    qu.push(bestNode.id);
                }
            }

            if (impossible)
            {
                cout << "impossible\n";
            }
        }
    }
    else
    {
        int queueCount = 0;
        vector<pii> QueueIndex(N + 1, {-1, -1});

        for (int i = 1; i <= N; i++)
        {
            if (QueueIndex[i].f != -1)
                continue;

            int qIndex = 0;

            QueueIndex[i].f = queueCount;
            QueueIndex[i].s = qIndex;
            qIndex++;

            queue<int> q;
            q.push(i);

            while (!q.empty())
            {
                int fr = q.front();
                q.pop();

                for (int j : adjAll[fr])
                {
                    if (QueueIndex[j].f != -1)
                        continue;

                    QueueIndex[j].f = queueCount;
                    QueueIndex[j].s = qIndex;
                    qIndex++;
                    q.push(j);
                    break;
                }
            }

            queueCount++;
        }

        /*for (int i = 1; i <= N; i++)
        {
            cout << "{" << QueueIndex[i].f << ", " << QueueIndex[i].s << "}\n";
        }*/

        for (int q = 0; q < Q; q++)
        {
            //cout << "q = " << q << '\n';
            if (QueueIndex[queries[q].f].f != QueueIndex[queries[q].s].f)
            {
                cout << "impossible\n";
                continue;
            }

            cout << abs(QueueIndex[queries[q].f].s - QueueIndex[queries[q].s].s) << '\n';
        }
    }


}

Compilation message (stderr)

events.cpp: In function 'int32_t main()':
events.cpp:86:13: warning: unused variable 'bestE' [-Wunused-variable]
   86 |         int bestE = -1;
      |             ^~~~~
events.cpp:87:13: warning: unused variable 'bestId' [-Wunused-variable]
   87 |         int bestId = -1;
      |             ^~~~~~

• Subtask 1: 0 / 10
• Subtask 2: 10 / 10
• Subtask 3: 0 / 15
• Subtask 4: 0 / 15
• Subtask 5: 0 / 20
• Subtask 6: 0 / 30