Submission #459500

#	Time	Username	Problem	Language	Result	Execution time	Memory
459500		S920105123	Port Facility (JOI17_port_facility)	C++14	100 / 100	1316 ms	180408 KiB

port_facility

#include <bits/stdc++.h>
#define LL long long
#define PII pair<int, int>
const LL MOD = (LL) 1e9 + 7;
const int MAXN = 1000005;
using namespace std;

struct Interval {
	int l, r;
};

struct DSU {
	int pa[2*MAXN], sz[2*MAXN], rmost[2*MAXN];
	void init(int n) {
		for (int i = 1; i <= n; i++) {
			sz[i] = 1;
			pa[i] = i;
			rmost[i] = i;
		}
	}
	int find(int x) {
		return x == pa[x] ? x : pa[x] = find(pa[x]);
	}
	int get_rmost(int x) {
		return rmost[find(x)];
	}
	int merge(int x, int y) {
		x = find(x); y = find(y);
		if (x == y) return 0;
		if (sz[x] < sz[y]) swap(x, y);
		sz[x] += sz[y];
		pa[y] = x;
		rmost[x] = max(rmost[x], rmost[y]);
		return 1;
	}
} U_nxt, U_jmp;

int n, col[MAXN], id[MAXN];
vector<int> G[MAXN];
Interval I[MAXN];

void add_edge(int u, int v) {
	G[u].push_back(v);
	G[v].push_back(u);
}

int dfs(int v, int c) {
	int ok = 1;
	col[v] = c;
	for (int to : G[v]) {
		if (col[to] == -1) {
			ok &= dfs(to, c ^ 1);
		}
		else {
			ok &= (col[to] != col[v]);
		}
	}
	return ok;
}

int main() {
	ios_base::sync_with_stdio(0); cin.tie(0);
	cin >> n;
	U_jmp.init(2 * n + 1);
	U_nxt.init(2 * n + 1);
	for (int i = 1; i <= n; i++) {
		cin >> I[i].l >> I[i].r;
	}
	sort(I + 1, I + 1 + n, [&] (Interval a, Interval b) {
		return a.l < b.l;
	});
	for (int i = 1; i <= n; i++) {
		U_jmp.merge(I[i].l, I[i].l + 1);
		U_nxt.merge(I[i].l, I[i].l + 1);
		id[I[i].l] = id[I[i].r] = i;
	}
	
	for (int i = n; i >= 1; i--) {
		U_nxt.merge(I[i].r, I[i].r + 1);
		int pre = -1, cur = U_nxt.get_rmost(I[i].l);
		while (cur < I[i].r) {
			add_edge(id[cur], i);
			if (pre != -1) {
				U_jmp.merge(pre, cur);
			}
			pre = cur;
			cur = U_jmp.get_rmost(cur);
			cur = U_nxt.get_rmost(cur + 1);
		}
	}
	
	int cc = 0;
	fill(col + 1, col + 1 + n, -1);
	for (int i = 1; i <= n; i++) {
		if (col[i] == -1) {
			if (!dfs(i, 0)) {
				cout << "0\n";
				return 0;
			}
			cc++;
		}
	}
	LL ans = 1;
	for (int i = 0; i < cc; i++) {
		ans = ans * 2 % MOD;
	}
	cout << ans << '\n';
	return 0;
}

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