Submission #642490

#	Time	Username	Problem	Language	Result	Execution time	Memory
642490		FedShat	Usmjeri (COCI17_usmjeri)	C++17	0 / 140	792 ms	262144 KiB

usmjeri

#include <bits/stdc++.h>

using namespace std;
using ll = long long;
constexpr int INF = numeric_limits<int>::max() / 2;
constexpr ll INFLL = numeric_limits<ll>::max() / 2;

template<class T>
istream &operator>>(istream &is, vector<T> &a) {
    for (auto &i : a) {
        is >> i;
    }
    return is;
}

constexpr int mod = 1e9 + 7;

struct BinaryJumps {
    static constexpr int k = 20;
    vector<vector<int>> up;
    vector<int> depth;

    BinaryJumps() {
    }

    BinaryJumps(int n) {
        up.resize(k, vector<int>(n));
        depth.resize(n);
    }

    void add_leaf(int v, int p) {
        up[0][v] = p;
        depth[v] = depth[p] + 1;
        for (int i = 1; i < k; ++i) {
            up[i][v] = up[i - 1][up[i - 1][v]];
        }
    }

    int up_k(int v, int d) {
        for (int i = k - 1; i >= 0; --i) {
            if (d >= (1 << i)) {
                v = up[i][v];
                d -= (1 << i);
            }
        }
        return v;
    }

    int LCA(int u, int v) {
        if (depth[u] < depth[v]) {
            swap(u, v);
        }
        u = up_k(u, depth[u] - depth[v]);
        for (int i = k - 1; i >= 0; --i) {
            if (up[i][u] != up[i][v]) {
                u = up[i][u];
                v = up[i][v];
            }
        }
        if (u == v) {
            return u;
        }
        return up[0][u];
    }
};

vector<vector<int>> g;
vector<int> par;
BinaryJumps t;

void dfs(int v, int p) {
    par[v] = p;
    for (auto u : g[v]) {
        if (u != p) {
            t.add_leaf(u, v);
            dfs(u, v);
        }
    }
}

vector<vector<pair<int, int>>> gr;
vector<int> color;
bool ok = 1;

void dfs2(int v) {
    for (auto [u, c] : gr[v]) {
        int cur = (c ? color[v] : color[v] ^ 1);
        if (color[u] == -1) {
            color[u] = cur;
            dfs2(u);
        } else {
            if (color[u] != cur) {
                ok = 0;
            }
        }
    }
}

int main() {
    cin.tie(0)->sync_with_stdio(0);
#ifdef __APPLE__
    freopen("input.txt", "r", stdin);
#endif
    int n, q;
    cin >> n >> q;
    g.resize(n);
    for (int i = 0; i < n - 1; ++i) {
        int u, v;
        cin >> u >> v;
        --u;
        --v;
        g[u].push_back(v);
        g[v].push_back(u);
    }
    t = BinaryJumps(n);
    par.resize(n);
    dfs(0, -1);
    gr.resize(n);
    auto add_edge = [&](int u, int v, int c) {
        gr[u].push_back({v, c});
        gr[v].push_back({u, c});
    };
    while (q--) {
        int u, v;
        cin >> u >> v;
        --u;
        --v;
        if (t.depth[u] < t.depth[v]) {
            swap(u, v);
        }
        int l = t.LCA(u, v);
        if (l == v) {// verticals
            int curu = u;
            while (par[curu] != l) {
                add_edge(curu, par[curu], 1);// equal
                curu = par[curu];
            }
        } else {
            int curu = u;
            while (par[curu] != l) {
                add_edge(curu, par[curu], 1);// equal
                curu = par[curu];
            }
            int curv = u;
            while (par[curv] != l) {
                add_edge(curv, par[curv], 1);// equal
                curv = par[curv];
            }
            add_edge(curu, curv, 0);
        }
    }
    int ans = 1;
    color.resize(n, -1);
    for (int i = 1; i < n; ++i) {
        if (color[i] == -1) {
            color[i] = 0;
            dfs2(i);
            ans = (ans * 2ll) % mod;
        }
    }
    if (!ok) {
        cout << "0\n";
    } else {
        cout << ans << "\n";
    }
}

• Subtask 1: 0 / 14
• Subtask 2: 0 / 14
• Subtask 3: 0 / 14
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• Subtask 10: 0 / 14