Submission #549008

#	Time	Username	Problem	Language	Result	Execution time	Memory
549008		SmolBrain	Usmjeri (COCI17_usmjeri)	C++17	0 / 140	110 ms	262144 KiB

usmjeri

// Om Namah Shivaya
// GM in 109 days

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;

template <class T> using Tree = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;

typedef long long int ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;

#define fastio ios_base::sync_with_stdio(false); cin.tie(NULL)
#define endl '\n'
#define pb push_back
#define conts continue
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define yes cout << "YES" << endl
#define no cout << "NO" << endl
#define ff first
#define ss second
#define ceil2(x,y) ((x+y-1) / (y))
#define sz(a) a.size()
#define setbits(x) __builtin_popcountll(x)
#ifndef ONLINE_JUDGE
#define debug(x) cout << #x <<" = "; print(x); cout << endl
#else
#define debug(x)
#endif

#define rep(i,n) for(int i = 0; i < n; ++i)
#define rep1(i,n) for(int i = 1; i <= n; ++i)
#define rev(i,s,e) for(int i = s; i >= e; --i)
#define trav(i,a) for(auto &i : a)

bool iseven(ll n) {if ((n & 1) == 0) return true; return false;}

void print(ll t) {cout << t;}
void print(int t) {cout << t;}
void print(string t) {cout << t;}
void print(char t) {cout << t;}
void print(double t) {cout << t;}
void print(ld t) {cout << t;}

template <class T, class V> void print(pair <T, V> p);
template <class T> void print(vector <T> v);
template <class T> void print(set <T> v);
template <class T, class V> void print(map <T, V> v);
template <class T> void print(multiset <T> v);
template <class T, class V> void print(pair <T, V> p) {cout << "{"; print(p.ff); cout << ","; print(p.ss); cout << "}";}
template <class T> void print(vector <T> v) {cout << "[ "; for (T i : v) {print(i); cout << " ";} cout << "]";}
template <class T> void print(set <T> v) {cout << "[ "; for (T i : v) {print(i); cout << " ";} cout << "]";}
template <class T> void print(multiset <T> v) {cout << "[ "; for (T i : v) {print(i); cout << " ";} cout << "]";}
template <class T, class V> void print(map <T, V> v) {cout << "[ "; for (auto i : v) {print(i); cout << " ";} cout << "]";}
template<typename T> void amin(T &a, T b) { a = min(a, b); }
template<typename T> void amax(T &a, T b) { a = max(a, b); }

void usaco(string filename) {
    freopen((filename + ".in").c_str(), "r", stdin);
    freopen((filename + ".out").c_str(), "w", stdout);
}

const int MOD = 1e9 + 7;
const int maxn = 3e5 + 5;
const int inf1 = 1e9 + 5;
const ll inf2 = ll(1e18) + 5;

vector<int> adj[maxn];

struct lca_algo {
    // LCA template (for graphs with 1-based indexing)

    int LOG = 1;
    vector<int> depth;
    vector<vector<int>> up;

    lca_algo() {

    }

    lca_algo(int n) {
        lca_init(n);
    }

    void lca_init(int n) {
        while ((1 << LOG) < n) LOG++;
        up = vector<vector<int>>(n + 1, vector<int>(LOG));
        depth = vector<int>(n + 1);

        lca_dfs(1, -1);
    }

    void lca_dfs(int node, int par) {
        trav(child, adj[node]) {
            if (child == par) conts;

            up[child][0] = node;
            rep1(j, LOG - 1) {
                up[child][j] = up[up[child][j - 1]][j - 1];
            }

            depth[child] = depth[node] + 1;

            lca_dfs(child, node);
        }
    }

    int lift(int u, int k) {
        rep(j, LOG) {
            if (k & (1 << j)) {
                u = up[u][j];
            }
        }

        return u;
    }

    int query(int u, int v) {
        if (depth[u] < depth[v]) swap(u, v);
        int k = depth[u] - depth[v];
        u = lift(u, k);

        if (u == v) return u;

        rev(j, LOG - 1, 0) {
            if (up[u][j] != up[v][j]) {
                u = up[u][j];
                v = up[v][j];
            }
        }

        u = up[u][0];
        return u;
    }
};

vector<int> parent(maxn, -1);

void dfs(int node, int par) {
    parent[node] = par;

    trav(child, adj[node]) {
        if (child == par) conts;
        dfs(child, node);
    }
}

void solve(int test_case)
{
    int n, m; cin >> n >> m;
    int edge[n + 1][n + 1];
    memset(edge, 0, sizeof edge);

    rep1(i, n - 1) {
        int u, v; cin >> u >> v;
        adj[u].pb(v), adj[v].pb(u);
    }

    lca_algo LCA(n);
    dfs(1, -1);

    int ans = 1;

    while (m--) {
        int u, v; cin >> u >> v;
        int ou = u, ov = v;

        int lca = LCA.query(u, v);
        int one1 = 0, two1 = 0, one2 = 0, two2 = 0;

        while (u != lca) {
            int p = parent[u];
            if (edge[u][p] == 1) one1++;
            else if (edge[u][p] == 2) two1++;
            u = p;
        }

        while (v != lca) {
            int p = parent[v];
            if (edge[v][p] == 1) one2++;
            else if (edge[v][p] == 2) two2++;
            v = p;
        }

        u = ou, v = ov;

        if (one1 == 0 and one2 == 0 and two1 == 0 and two2 == 0) {
            ans = (ans * 2) % MOD;

            while (u != lca) {
                int p = parent[u];

                if (!edge[u][p]) {
                    edge[u][p] = 1;
                    edge[p][u] = 1;
                }

                u = p;
            }

            while (v != lca) {
                int p = parent[v];

                if (!edge[v][p]) {
                    edge[v][p] = 2;
                    edge[p][v] = 2;
                }

                v = p;
            }
        }
        else {
            if ((one1 and one2) or (two1 and two2)) {
                cout << 0 << endl;
                return;
            }

            if (one1 or two2) {
                while (u != lca) {
                    int p = parent[u];

                    if (!edge[u][p]) {
                        edge[u][p] = 1;
                        edge[p][u] = 1;
                    }

                    u = p;
                }

                while (v != lca) {
                    int p = parent[v];

                    if (!edge[v][p]) {
                        edge[v][p] = 2;
                        edge[p][v] = 2;
                    }

                    v = p;
                }
            }
            else {
                while (u != lca) {
                    int p = parent[u];

                    if (!edge[u][p]) {
                        edge[u][p] = 2;
                        edge[p][u] = 2;
                    }

                    u = p;
                }

                while (v != lca) {
                    int p = parent[v];

                    if (!edge[v][p]) {
                        edge[v][p] = 1;
                        edge[p][v] = 1;
                    }

                    v = p;
                }
            }
        }
    }

    rep1(u, n) {
        trav(v, adj[u]) {
            if (u != parent[v]) conts;

            if (!edge[u][v]) {
                ans = (ans * 2) % MOD;
            }
        }
    }

    cout << ans << endl;
}

int main()
{
    fastio;

    int t = 1;
    // cin >> t;
    rep1(i, t) {
        solve(i);
    }

    return 0;
}

Compilation message (stderr)

usmjeri.cpp: In function 'void usaco(std::string)':
usmjeri.cpp:64:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   64 |     freopen((filename + ".in").c_str(), "r", stdin);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
usmjeri.cpp:65:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   65 |     freopen((filename + ".out").c_str(), "w", stdout);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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