제출 #927138

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
927138		12345678	Usmjeri (COCI17_usmjeri)	C++17	28 / 140	311 ms	73300 KiB

usmjeri

#include <bits/stdc++.h>

using namespace std;

const int nx=3e5+5, kx=19, mod=1e9+7;

int n, m, u, v, lvl[nx], pa[nx][kx], a, b, l, up[nx], dn[nx], res=1, cnt;
vector<int> d[nx];

void dfs(int u, int p)
{
    lvl[u]=lvl[p]+1;
    pa[u][0]=p;
    for (int i=1; i<kx; i++) pa[u][i]=pa[pa[u][i-1]][i-1];
    for (auto v:d[u]) if (v!=p) dfs(v, u);
}

int lca(int u, int v)
{
    if (lvl[u]>lvl[v]) swap(u, v);
    for (int i=kx-1; i>=0; i--) if (lvl[pa[v][i]]>=lvl[u]) v=pa[v][i];
    if (u==v) return u;
    for (int i=kx-1; i>=0; i--) if (pa[u][i]!=pa[v][i]) u=pa[u][i], v=pa[v][i];
    return pa[u][0];
}

void dfs2(int u, int p)
{
    for (auto v:d[u]) if (v!=p) dfs2(v, u), up[u]+=up[v], dn[u]+=dn[v];
    if (up[u]&&dn[u]) res=0;
    else if (!up[u]&&!dn[u]) cnt++;
}

int main()
{
    cin.tie(NULL)->sync_with_stdio(false);
    cin>>n>>m;
    for (int i=1; i<n; i++) cin>>u>>v, d[u].push_back(v), d[v].push_back(u);
    dfs(1, 1);
    for (int i=1; i<=m; i++) cin>>a>>b, up[a]++, up[lca(a, b)]--, dn[b]++, dn[lca(a, b)]--;
    dfs2(1, 1);
    for (int i=1; i<=cnt; i++) res=(res*2)%mod;
    cout<<res;
}

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