Submission #943768

#	Time	Username	Problem	Language	Result	Execution time	Memory
943768		tmarcinkevicius	Event Hopping (BOI22_events)	C++14	10 / 100	1589 ms	414808 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; });
    }

    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";
        }
    }
}

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