Submission #721807

#	Time	Username	Problem	Language	Result	Execution time	Memory
721807		rshohruh	Event Hopping (BOI22_events)	C++14	0 / 100	1550 ms	7176 KiB

events

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

const int MAXN = 1e5 + 5;

int N, Q;
vector<pair<int, int>> events;
vector<int> graph[MAXN];
vector<int> switches;

int main() {
    cin >> N >> Q;
    events.resize(N + 1);
    for (int i = 1; i <= N; i++) {
        cin >> events[i].first >> events[i].second;
    }
    sort(events.begin() + 1, events.end());
    for (int i = 1; i <= N; i++) {
        for (int j = i + 1; j <= N; j++) {
            if (events[j].first <= events[i].second) {
                graph[i].push_back(j);
            } else {
                break;
            }
        }
    }
    while (Q--) {
        int s, e;
        cin >> s >> e;
        switches.assign(N + 1, -1);
        priority_queue<pair<int, int>, vector<pair<int, int>>, greater<pair<int, int>>> pq;
        pq.push({0, s});
        switches[s] = 0;
        while (!pq.empty()) {
            int u = pq.top().second;
            int w = pq.top().first;
            pq.pop();
            if (u == e) {
                cout << switches[e] << endl;
                break;
            }
            for (int i = 0; i < graph[u].size(); i++) {
                int v = graph[u][i];
                if (switches[v] == -1 || switches[v] > switches[u] + 1) {
                    switches[v] = switches[u] + 1;
                    pq.push({switches[v], v});
                }
            }
        }
        if (switches[e] == -1) {
            cout << "impossible" << endl;
        }
    }
    return 0;
}

Compilation message (stderr)

events.cpp: In function 'int main()':
events.cpp:42:31: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   42 |             for (int i = 0; i < graph[u].size(); i++) {
      |                             ~~^~~~~~~~~~~~~~~~~
events.cpp:36:17: warning: unused variable 'w' [-Wunused-variable]
   36 |             int w = pq.top().first;
      |                 ^

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