Submission #1216566

#	Time	Username	Problem	Language	Result	Execution time	Memory
1216566		baotoan655	Alternating Current (BOI18_alternating)	C++20	0 / 100	42 ms	14788 KiB

alternating

#include <bits/stdc++.h>
#define file(name)  if (fopen(name".inp", "r")) { freopen(name".inp", "r", stdin); freopen(name".out", "w", stdout); }
#define FOR(i, a, b) for(int i = (a); i <= (b); ++i)
#define REV(i, b, a) for(int i = (b); i >= (a); --i)
#define REP(i, n) for(int i = 0; i < (n); ++i)
#define ll long long
#define fi first
#define se second
#define BIT(x, i) ((x) >> (i) & 1)
using namespace std;
const int N = 1e5 + 5;
int n, m;
struct dizi {
	int l, r, id;
	bool operator < (const dizi& o) const {
		int sza = r - l;
		if (l > r) sza += n;
		int szb = o.r - o.l;
		if (o.l > o.r) szb += n;
		return sza > szb;
	}
} seg[N];
vector<int> v[N];
bool in[N];
vector<int> adj[N];
int col[N], ans[N];
bool chk(int v, int c = 1) {
	if (col[v]) return col[v] == c;
	col[v] = c;
	for (auto& x : adj[v]) {
		if (!chk(x, 3 - c)) return false;
	}
	return true;
}
void solve(int tc) {
	cin >> n >> m;
	set<int> se;
	for (int i = 0; i < n; i++) se.insert(i);
	for (int i = 0; i < m; i++) {
		cin >> seg[i].l >> seg[i].r;
		seg[i].l--, seg[i].r--;
		seg[i].id = i;
	}
	sort(seg, seg + m);
	for (int i = 0; i < m; i++) {
		int l = seg[i].l, r = seg[i].r;
		vector<int> rem;
		if (l <= r) {
			auto x = se.lower_bound(l);
			auto y = se.upper_bound(r);
			for (; x != y; x++) {
				v[*x].push_back(i);
				if ((int)v[*x].size() == 3) rem.push_back(*x);
			}
		} else {
			auto x = se.lower_bound(l);
			for (; x != se.end(); x++) {
				v[*x].push_back(i);
				if ((int)v[*x].size() == 3) rem.push_back(*x);
			}
			x = se.begin();
			auto y = se.upper_bound(r);
			for (; x != y; x++) {
				v[*x].push_back(i);
				if ((int)v[*x].size() == 3) rem.push_back(*x);
			}
		}
		for (auto& x : rem) se.erase(x);
	}
	for (int i = 0; i < n; i++) {
		if ((int)v[i].size() <= 1) {
			cout << "impossible\n";
			return;
		}
	}
	for (int i = 0; i < n; i++) {
		if ((int)v[i].size() == 2) {
			in[v[i][0]] = in[v[i][1]] = 1;
			adj[v[i][0]].push_back(v[i][1]);
			adj[v[i][1]].push_back(v[i][0]);
		}
	}
	for (int i = 0; i < m; i++) {
		if (in[i] && !col[i]) {
			if (!chk(i)) {
				cout << "impossible\n";
				return;
			}
		}
		cout << col[i] - 1;
	}
	return;
}
int32_t main() {
	ios_base::sync_with_stdio(false);
	cin.tie(0);
	cout.tie(0);
//    file("A") else file("task");
	int tc = 1;
//     cin >> tc;
	for(int i = 1; i <= tc; ++i) solve(i);
	return (0);
}

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