Submission #404255

#	Time	Username	Problem	Language	Result	Execution time	Memory
404255		penguinhacker	Usmjeri (COCI17_usmjeri)	C++14	140 / 140	518 ms	81384 KiB

usmjeri

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

#define ll long long
#define ar array

const int mxN=3e5, M=1e9+7;
int n, m, d[mxN], anc[mxN][19], dp[mxN], p[mxN], col[mxN];
vector<int> adj[mxN], adj2[mxN];
vector<ar<int, 2>> bad;

void dfs1(int u=0) {
	for (int i=1; i<19; ++i)
		anc[u][i]=anc[anc[u][i-1]][i-1];
	for (int v : adj[u]) {
		adj[v].erase(find(adj[v].begin(), adj[v].end(), u));
		d[v]=d[u]+1, anc[v][0]=u;
		dfs1(v);
	}
}

int lca(int u, int v) {
	if (d[u]>d[v])
		swap(u, v);
	for (int i=18; ~i; --i)
		if (d[u]<=d[v]-(1<<i))
			v=anc[v][i];
	if (u==v)
		return u;
	for (int i=18; ~i; --i)
		if (anc[u][i]^anc[v][i])
			u=anc[u][i], v=anc[v][i];
	return anc[u][0];
}

int lift(int u, int k) {
	int r=u;
	for (int i=0; i<19; ++i)
		if (k&(1<<i))
			r=anc[r][i];
	return r;
}

void dfs2(int u=0) {
	for (int v : adj[u])
		dfs2(v), dp[u]+=dp[v];
}

int find(int i) {
	return i^p[i]?p[i]=find(p[i]):i;
}

void merge(int u, int v) {
	u=find(u), v=find(v);
	if (u==v)
		return;
	p[v]=u;
}

void dfs3(int u, int c) {
	col[u]=c;
	for (int v : adj2[u]) {
		if (col[v]==-1)
			dfs3(v, c^1);
		else if (col[u]==col[v]) {
			cout << 0;
			exit(0);
		}
	}
}

int main() {
	ios::sync_with_stdio(0);
	cin.tie(0);
	cin >> n >> m;
	for (int i=1; i<n; ++i) {
		int u, v;
		cin >> u >> v, --u, --v;
		adj[u].push_back(v);
		adj[v].push_back(u);
	}
	dfs1();
	for (int i=0; i<m; ++i) {
		int u, v;
		cin >> u >> v, --u, --v;
		int uv=lca(u, v), lu=-1, lv=-1;
		if (u^uv) {
			lu=lift(u, d[u]-d[uv]-1);
			++dp[u], --dp[lu];
		}
		if (v^uv) {
			lv=lift(v, d[v]-d[uv]-1);
			++dp[v], --dp[lv];
		}
		if (u^uv&&v^uv)
			bad.push_back({lu, lv});
	}
	dfs2();
	iota(p, p+n, 0);
	for (int i=1; i<n; ++i)
		if (dp[i])
			merge(i, anc[i][0]);
	for (ar<int, 2>& a : bad) {
		if (dp[a[0]]&&dp[a[1]]) {
			cout << 0;
			return 0;
		}
		int u=find(a[0]), v=find(a[1]);
		adj2[u].push_back(v);
		adj2[v].push_back(u);
	}
	memset(col, -1, sizeof(col));
	int ans=1;
	for (int i=1; i<n; ++i) {
		if (i^p[i]||col[i]^-1)
			continue;
		dfs3(i, 0);
		ans=2*ans%M;
	}
	cout << ans;
	return 0;
}

• Subtask 1: 14 / 14
• Subtask 2: 14 / 14
• Subtask 3: 14 / 14
• Subtask 4: 14 / 14
• Subtask 5: 14 / 14
• Subtask 6: 14 / 14
• Subtask 7: 14 / 14
• Subtask 8: 14 / 14
• Subtask 9: 14 / 14
• Subtask 10: 14 / 14