Submission #937709

#	Time	Username	Problem	Language	Result	Execution time	Memory
937709		LucaIlie	Event Hopping (BOI22_events)	C++17	10 / 100	1595 ms	8400 KiB

events

#include <bits/stdc++.h>

using namespace std;

const int MAX_N = 1e5;
const int MAX_T = 2e5;

struct event {
    int i, s, e;
};

int prv[MAX_N];
event events[MAX_N];
map<int, int> nrm;

bool canSwitch( event a, event b ) {
    return (b.s <= a.e && a.e <= b.e);
}

int main() {
    int n, q;

    cin >> n >> q;
    for ( int i = 1; i <= n; i++ ) {
        cin >> events[i].s >> events[i].e;
        nrm[events[i].s] = nrm[events[i].e] = 1;
        events[i].i = i + 1;
    }
    int t = 0;
    for ( auto p: nrm )
        nrm[p.first] = ++t;
    for ( int i = 1; i <= n; i++ ) {
        events[i].s = nrm[events[i].s];
        events[i].e = nrm[events[i].e];
    }

    for ( int i = 1; i <= n; i++ ) {
        prv[i] = i;
        for ( int j = 1; j <= n; j++ ) {
            if ( canSwitch( events[j], events[i] )  ) {
                if ( events[j].s < events[prv[i]].s )
                    prv[i] = j;
            }
        }
    }

    while ( q-- ) {
        int s, e, x = 1;
        cin >> s >> e;

        int i = e;
        while ( events[i].s > events[s].e && prv[i] != i ) {
            i = prv[i];
            x++;
        }


        if ( s == e )
            cout << 0 << "\n";
        else if ( canSwitch( events[s], events[i] ) )
            cout << x << "\n";
        else
            cout << "impossible\n";
    }

    return 0;
}

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