Submission #656163

#TimeUsernameProblemLanguageResultExecution timeMemory
656163ilia_rrPort Facility (JOI17_port_facility)C++14
0 / 100
0 ms340 KiB
// بِسْمِ اللَّهِ الرَّحْمَنِ الرَّحِيمِ
// Written by Ilia Rahbar

// #pragma GCC optimize ("O3,no-stack-protector,unroll-loops,fast-math")
// #pragma GCC target ("abm,bmi,bmi2,tbm,avx2")

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

#define int int64_t
#define ai(x) array <int, x>
#define F first 
#define S second

const int MOD = 1e9 + 7, N = 1e6 + 100;

ai(2) a[N];

int n, d[N], l[N * 2], vs[N], c, ans = 1;

set <int> s;

set <int> :: iterator itr;

int32_t main()
{
    ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
    
    cin >> n;

    for (int i = 0; i < n; i++)
       cin >> a[i][0] >> a[i][1]; 

    sort(a, a+n);

    for (int i = 0; i < n; i++)
    {
        l[a[i][0]] = i+1;
        l[a[i][1]] = i+1;
    }

    for (int i = 1; i <= n * 2; i++)
    {
        if (vs[l[i]])
        {
            s.erase(l[i]);

            if (!d[l[i]])
            {
                d[l[i]] = 1;

                c++;
            }

            itr = s.end();

            while (s.size())
            {
                itr--;

                if (*itr < l[i])
                    break;

                if (d[*itr] && d[*itr] != 3 - d[l[i]])
                {
                    cout << 0;

                    return 0;
                }

                d[*itr] = 3 - d[l[i]];

                if (itr == s.begin())
                    break;
            }
        }

        else
        {
            vs[l[i]] = 1;

            s.insert(l[i]);
        }
    }
    
    for (int i = 0; i < c; i++)
        ans = (ans * 2) % MOD;

    cout << ans;
}
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