Submission #1210996

#	Time	Username	Problem	Language	Result	Execution time	Memory
1210996		madamadam3	Port Facility (JOI17_port_facility)	C++20	22 / 100	2009 ms	1114112 KiB

port_facility

#include <bits/stdc++.h>

using namespace std;

#define int long long int

struct Event {
    int time, box_id;
    bool is_remove;

    const bool operator<(const Event &other) {
        return time < other.time;
    }
};

const int MAXN = 1'000'001;
const int MOD = 1'000'000'007;
int n;

int A[MAXN], B[MAXN];
vector<Event> events;

int modexp(int a, int p) {
    if (p == 0) return 1;
    if (p == 1) return a;

    int ans = modexp(a, p / 2);
    ans %= MOD;

    ans *= ans;
    ans %= MOD;

    if (p % 2 == 1) ans *= a;
    ans %= MOD;

    return ans % MOD;
}

void solve() {
    int ways = 0;
    vector<vector<int>> adj(n, vector<int>());
    set<pair<int,int>> active; 

    // for (int i = 0; i < n; i++) {
    //     for (int j = i+1; j < n; j++) {
    //         int ci = i, cj = j;
    //         if (A[ci] > A[cj]) swap(ci, cj);
    //         if (A[ci] < A[cj] && A[cj] < B[ci] && B[ci] < B[cj]) {
    //             adj[ci].push_back(cj);
    //             adj[cj].push_back(ci);
    //         }
    //     }
    // }

    for (auto &E : events) {
        int idx = E.box_id;
        if (!E.is_remove) {
            auto it_lo = active.upper_bound({ A[idx], -1 });
            auto it_hi = active.lower_bound({ B[idx], -1 }); 

            vector<pair<int,int>> toLink;
            for (auto it = it_lo; it != it_hi; ++it) {
                toLink.push_back(*it);
            }

            for (auto &pr : toLink) {
                int other = pr.second;
                adj[other].push_back(idx);
                adj[idx].push_back(other);
            }

            active.insert({ B[idx], idx });
        } else {
            active.erase({ B[idx], idx });
        }
    }


    int cmps = 0; bool bipartite = true;
    vector<int> colour(n, -1);
    queue<int> q;

    for (int i = 0; i < n; i++) {
        if (colour[i] != -1 || !bipartite) continue;
        cmps++;

        q.push(i);
        colour[i] = 1;

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

            for (auto &el : adj[cur]) {
                if (colour[el] == colour[cur]) {
                    bipartite = false;
                    break;
                } else if (colour[el] == -1) {
                    colour[el] = colour[cur] == 1 ? 2 : 1;
                    q.push(el);
                }
            }

            if (!bipartite) break;
        }
    }

    ways = bipartite ? modexp(2, cmps) % MOD : 0;
    cout << ways;
}

signed main() {
    cin.tie(0)->sync_with_stdio(0);
    
    cin >> n;
    for (int i = 0; i < n; i++) {
        cin >> A[i] >> B[i];
    }

    for (int i = 0; i < n; i++) {
        events.push_back(Event {A[i], i, false});
        events.push_back(Event {B[i], i, true});
    }

    sort(events.begin(), events.end());

    solve();
    return 0;
}

• Subtask 1: 10 / 10
• Subtask 2: 12 / 12
• Subtask 3: 0 / 56
• Subtask 4: 0 / 22