Submission #210442

#	Time	Username	Problem	Language	Result	Execution time	Memory
210442		dolphingarlic	Port Facility (JOI17_port_facility)	C++14	100 / 100	1515 ms	77560 KiB

port_facility

#include <bits/stdc++.h>
#define FOR(i, x, y) for (int i = x; i < y; i++)
typedef long long ll;
using namespace std;

const ll MOD = 1e9 + 7;

pair<int, int> a[1000000];
int cmp[2000000], n;

int find(int A) {
    while (A != cmp[A]) cmp[A] = cmp[cmp[A]], A = cmp[A];
    return A;
}

bool onion(int A, int B) { cmp[find(A)] = find(B); }

int main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cin >> n;
    FOR(i, 0, n) cin >> a[i].first >> a[i].second;
    sort(a, a + n);

    iota(cmp, cmp + 2 * n, 0);

    set<pair<int, int>> s;
    FOR(i, 0, n) {
        while (s.size() && (*s.begin()).first < a[i].first) s.erase(s.begin());

        auto ub = s.upper_bound({a[i].second, n});
        if (ub != s.begin())
            for (ub--;; ub--) {
                onion(i, (*ub).second + n);
                onion(i + n, (*ub).second);
                if (find((*ub).second) == find((*s.begin()).second)) break;
                if (ub == s.begin()) break;
            }
        s.insert({a[i].second, i});
    }

    FOR(i, 0, n) if (find(i) == find(i + n)) return cout << 0, 0;
    ll cnt = 0, ans = 1;
    FOR(i, 0, 2 * n) if (find(i) == i) cnt++;
    FOR(i, 0, cnt / 2) ans = (ans * 2) % MOD;
    cout << ans;
    return 0;
}

Compilation message (stderr)

port_facility.cpp: In function 'bool onion(int, int)':
port_facility.cpp:16:52: warning: no return statement in function returning non-void [-Wreturn-type]
 bool onion(int A, int B) { cmp[find(A)] = find(B); }
                                                    ^

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