Submission #1229884

#	Time	Username	Problem	Language	Result	Execution time	Memory
1229884		Dedibeat	Usmjeri (COCI17_usmjeri)	C++20	28 / 140	270 ms	78904 KiB

usmjeri

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

int n, l;
vector<vector<int>> adj;

int timer;
vector<int> tin, tout, vis;
vector<vector<int>> up;

void dfs(int v, int p) {
    tin[v] = ++timer;
    up[v][0] = p;
    for (int i = 1; i <= l; ++i) {
        up[v][i] = up[ up[v][i-1] ][i-1];
    }
    for (int u : adj[v]) {
        if (u != p) {
            dfs(u, v);
        }
    }
    tout[v] = ++timer;
}

bool is_ancestor(int u, int v) {
    return tin[u] <= tin[v] && tout[u] >= tout[v];
}

int LCA(int u, int v) {
    if (is_ancestor(u, v)) return u;
    if (is_ancestor(v, u)) return v;
    for (int i = l; i >= 0; --i) {
        if (!is_ancestor(up[u][i], v)) {
            u = up[u][i];
        }
    }
    return up[u][0];
}

void preprocess(int root) {
    tin.assign(n + 1, 0);
    tout.assign(n + 1, 0);
    timer = 0;
    l = ceil(log2(n + 1));
    up.assign(n + 1, vector<int>(l + 1, 0));
    dfs(root, root);
}

static const int MAXN = 300005;
vector<pair<int,int>> g[MAXN];
int color[MAXN];

int dfs2(int v) {
    int ok = 1;
    //cout << "vis" << v << endl;
    for (auto [u, rel] : g[v]) {
        if (color[u] == 0) {
            color[u] = color[v] ^ rel;
            ok &= dfs2(u);
        } else if (color[u] != (color[v] ^ rel)) {
            return 0;
        }
    }
    return ok;
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    int m;
    cin >> n >> m;
    adj.assign(n + 1, {});
    
    for (int i = 0; i < n - 1; i++) {
        int u, v;
        cin >> u >> v;
        adj[u].push_back(v);
        adj[v].push_back(u);
    }
    
    preprocess(1);
    vis.assign(n + 1, 0);

    for (int i = 0; i < m; i++) {
        int a, b;
        cin >> a >> b;
        int lca = LCA(a, b);
        //cout << lca << endl;
        for (int v = a; v != lca; v = up[v][0]) {
            if (vis[v] || up[v][0] == lca) break;
            //cout << "at :" << v << " par :" << up[v][0] << endl;
            vis[v] = 1;
            g[v].emplace_back(up[v][0], 0);
            g[up[v][0]].emplace_back(v, 0);
        }
        for (int v = b; v != lca; v = up[v][0]) {
            if (vis[v] || up[v][0] == lca) break;
            //cout << "at :" << v << " par :" << up[v][0] << endl;
            vis[v] = 1;
            g[v].emplace_back(up[v][0], 0);
            g[up[v][0]].emplace_back(v, 0);
        }

        if(lca == a || lca == b) continue;
        
        g[a].emplace_back(b, 3);
        g[b].emplace_back(a, 3);
    }


    int cnt = 0;
    for (int i = 2; i <= n; i++) {
        if (color[i] == 0) {
            color[i] = 1;
            cnt++;
            //cout << i << endl;
            if (!dfs2(i)) {
                cout << "0\n";
                return 0;
            }
        }
    }

    const int MOD = 1e9 + 7;
    long long ans = 1;
    for (int i = 0; i < cnt; i++) {
        ans = (ans * 2) % MOD;
    }
    cout << ans << "\n";
    return 0;
}

• Subtask 1: 14 / 14
• Subtask 2: 14 / 14
• Subtask 3: 0 / 14
• Subtask 4: 0 / 14
• Subtask 5: 0 / 14
• Subtask 6: 0 / 14
• Subtask 7: 0 / 14
• Subtask 8: 0 / 14
• Subtask 9: 0 / 14
• Subtask 10: 0 / 14