Submission #120383

#	Time	Username	Problem	Language	Result	Execution time	Memory
120383		tinder	Port Facility (JOI17_port_facility)	C++14	78 / 100	6094 ms	466492 KiB

port_facility

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

using ii = pair<int, int>;
const int maxn = 2e6 + 6;
const int mod = 1e9 + 7;

int n, s[maxn], t[maxn];
vector<int> g[maxn], w[maxn];

void add_edge(int u, int v, int col) {
	w[u].emplace_back(col);
	w[v].emplace_back(col);
	g[u].emplace_back(v);
	g[v].emplace_back(u);
}

struct info {
	int x, id;
	info () {}
	info (int _x, int _id) {
		x = _x, id = _id;
	}
	bool operator < (const info &that) const {
		return x < that.x;
	}
};
vector<info> ft[maxn];
vector<int> p[maxn];

void insert(int i, info j) {
	for(; i <= (n << 1); i += i & -i) {
		ft[i].emplace_back(j);
	}
}

void update(int i, int l, int r, int id) {
	for(; i > 0; i -= i & -i) {
		int L = lower_bound(ft[i].begin(), ft[i].end(), info(l, 69)) - ft[i].begin();
		int R = upper_bound(ft[i].begin(), ft[i].end(), info(r, 69)) - ft[i].begin();
		if(R > L) {
			R--;
			p[i][L]++;
			p[i][R]--;
			add_edge(id, ft[i][L].id, 1);
		}
	}
}

int vis[maxn];
int col[maxn];

void dfs(int u) {
	vis[u] = 1;
	for(int i = 0; i < g[u].size(); i++) {
		int v = g[u][i], c = w[u][i];
		if(!vis[v]) {
			col[v] = col[u] ^ c;
			dfs(v);
		}
	}
}

bool valid() {
	vector<int> id(2 * n + 5), op(2 * n + 5);
	for(int i = 1; i <= n; i++) {
		id[s[i]] = i, op[s[i]] = +1;
		id[t[i]] = i, op[t[i]] = -1;
	}
	vector<int> A, B;
	for(int i = 1; i <= (2 * n); i++) {
		if(op[i] == +1) {
			col[id[i]] ? A.push_back(id[i]) : B.push_back(id[i]);
		} else {
			vector<int> &w0t = col[id[i]] ? A : B;
			if(w0t.empty() or w0t.back() != id[i]) {
				return false;
			} else {
				w0t.pop_back();
			}
		}
	} return true;
}

int main(int argc, char const *argv[])
{
	// freopen("in", "r", stdin);
	scanf("%d", &n);
	for(int i = 1; i <= n; i++) {
		scanf("%d %d", &s[i], &t[i]);
	}
	for(int i = 1; i <= n; i++) {
		insert(s[i], info(t[i], i));
	}
	for(int i = 1; i <= (n << 1); i++) {
		sort(ft[i].begin(), ft[i].end());
		p[i].assign(ft[i].size(), 0);
	}
	for(int i = 1; i <= n; i++) {
		update(s[i] - 1, s[i] + 1, t[i] - 1, i);
	}
	for(int i = 1; i <= (n << 1); i++) {
		for(int j = 1; j < p[i].size(); j++) {
			p[i][j] += p[i][j - 1];
		}
		for(int j = 0; j < (int)p[i].size() - 1; j++) {
			if(p[i][j]) {
				add_edge(ft[i][j].id, ft[i][j + 1].id, 0);
			}
		}
	}
	int ans = 1;
	for(int i = 1; i <= n; i++) {
		if(!vis[i]) {
			ans <<= 1;
			if(ans >= mod) {
				ans -= mod;
			}
			dfs(i);
		}
	}
	if(valid()) {
		printf("%d\n", ans);
	} else {
		puts("0");
	}
	return 0;
}

Compilation message (stderr)

port_facility.cpp: In function 'void dfs(int)':
port_facility.cpp:55:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i = 0; i < g[u].size(); i++) {
                 ~~^~~~~~~~~~~~~
port_facility.cpp: In function 'int main(int, const char**)':
port_facility.cpp:103:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(int j = 1; j < p[i].size(); j++) {
                  ~~^~~~~~~~~~~~~
port_facility.cpp:88:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d", &n);
  ~~~~~^~~~~~~~~~
port_facility.cpp:90:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d %d", &s[i], &t[i]);
   ~~~~~^~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 10 / 10
• Subtask 2: 12 / 12
• Subtask 3: 56 / 56
• Subtask 4: 0 / 22