Submission #532712

#	Time	Username	Problem	Language	Result	Execution time	Memory
532712		fatemetmhr	Alternating Current (BOI18_alternating)	C++17	32 / 100	374 ms	9700 KiB

alternating

#include <bits/stdc++.h>

using namespace std;

typedef long long ll;

#define pb push_back

mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());


const int maxn5 = 2e5 + 10;

int a[maxn5], b[maxn5];
bool av[2][maxn5];
int n, m;
bool ty[maxn5];
vector <int> seg[maxn5], ex;

inline void kill(){
	cout << "impossible" << endl;
	exit(0);
}

inline void solve(){
	for(int i = 0; i < m; i++){
		seg[a[i]].pb(i);
	}
	int id1 = -1, id2 = -1;
	for(int i = 0; i < n; i++){
		if(b[id1] < i)
			id1 = -1;
		if(b[id2] < i)
			id2 = -1;
		while(!ex.empty() && b[ex.back()] < i)
			ex.pop_back();
		for(auto u : seg[i])
			ex.pb(u);
		if(id1 == -1){
			if(ex.empty())
				kill();
			id1 = ex.back();
			ty[id1] = true;
			ex.pop_back();
		}
		while(!ex.empty() && b[ex.back()] < i)
			ex.pop_back();
		if(id2 == -1){
			if(ex.empty())
				kill();
			id2 = ex.back();
			ex.pop_back();
		}
	}
	for(int i = 0; i < m; i++)
		cout << ty[i];
	cout << endl;
	exit(0);
}


int main(){
	ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);

	cin >> n >> m;
	for(int i = 0; i < m; i++){
		cin >> a[i] >> b[i];
		a[i]--;
		b[i]--;
	}

	if(max(n, m) > 20) 
		solve();

	for(int mask = 1; mask < (1 << m) - 1; mask++){
		memset(av, false, sizeof av);
		for(int i = 0; i < m; i++){
			int x = a[i];
			while(true){
				av[(mask >> i)&1][x] = true;
				if(x == b[i])
					break;
				x++;
				if(x == n)
					x = 0;
			}
		}
		bool re = true;
		for(int i = 0; i < n; i++)
			if(!av[0][i] || !av[1][i])
				re = false;
		if(re){
			for(int i = 0; i < m; i++)
				cout << ((mask >> i)&1);
			return cout << endl, 0;
		}
	}
	cout << "impossible" << endl;

}

• Subtask 1: 13 / 13
• Subtask 2: 0 / 20
• Subtask 3: 0 / 22
• Subtask 4: 19 / 19
• Subtask 5: 0 / 26