Submission #447256

#	Time	Username	Problem	Language	Result	Execution time	Memory
447256		ak2006	Railway (BOI17_railway)	C++14	100 / 100	164 ms	34288 KiB

railway

#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using vb = vector<bool>;
using vvb = vector<vb>;
using vi = vector<int>;
using vvi = vector<vi>;
using vl = vector<ll>;
using vvl = vector<vl>;
using vc = vector<char>;
using vvc = vector<vc>;
using vs = vector<string>;
const ll mod = 1e9 + 7,inf = 1e18;
#define pb push_back
#define fast ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
void setIO()
{
    fast;
}
int n = 1e5 + 5,m,k,TIMER;
vvi adj(n),anc(n,vi(21));
vi pref(n),in(n),out(n);
void dfs(int u,int p)
{
    in[u] = ++TIMER;
    anc[u][0] = p;
    for (int i = 1;i<=20;i++)anc[u][i] = anc[anc[u][i - 1]][i - 1];
    for (int v:adj[u]){
        if (v == p)continue;
        dfs(v,u);
    }
    out[u] = ++TIMER;
}
void dfs2(int u,int p)
{
    for (int v:adj[u]){
        if (v == p)continue;
        dfs2(v,u);
        pref[u] += pref[v];
    }
}
bool cmp(int a,int b)
{
    return in[a] <= in[b];
}
bool is_ancestor(int u,int v)
{
    return in[u] <= in[v] && out[u] >= out[v];
}
int LCA(int u,int v)
{
    if (in[u] > in[v])swap(u,v);
    if (is_ancestor(u,v))return u;
    for (int i = 20;i>=0;i--)
        if (!is_ancestor(anc[v][i],u))v = anc[v][i];
    return anc[v][0];
}
int main()
{
    setIO();
    cin>>n>>m>>k;
    vvi edges;
    vi ind(n + 1);
    for (int i = 1;i<n;i++){int u,v;cin>>u>>v;adj[u].pb(v),adj[v].pb(u);edges.pb({u,v});}
    dfs(1,1);
    while (m--){
        int num;
        cin>>num;
        vi vals(num);
        for (int i = 0;i<num;i++)cin>>vals[i];
        sort(vals.begin(),vals.end(),cmp);
        // for (int i = 0;i<num - 1;i++){
        //     cout<<vals[i]<<" "<<vals[i + 1]<<" "<<LCA(vals[i],vals[i + 1])<<'\n';
        // }
        // cout<<'\n';
        for (int i = 0;i<num;i++){
            int lca = LCA(vals[i],vals[(i + 1)%num]);
            pref[vals[i]]++;
            pref[vals[(i + 1)%num]]++;
            pref[lca] -= 2;
        }
    }
    dfs2(1,1);
    vi all;
    for (int i = 0;i<edges.size();i++){
        int u = edges[i][0],v = edges[i][1];
        if (in[u] > in[v])swap(u,v);
        ind[v] = i;
    }
    for (int i = 1;i<=n;i++)if (pref[i] >= 2 * k)all.pb(ind[i]);
    cout<<all.size()<<'\n';
    sort(all.begin(),all.end());
    for (auto it:all)cout<<it + 1<<" ";
    return 0;
}

Compilation message (stderr)

railway.cpp: In function 'int main()':
railway.cpp:85:21: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::vector<int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   85 |     for (int i = 0;i<edges.size();i++){
      |                    ~^~~~~~~~~~~~~

• Subtask 1: 8 / 8
• Subtask 2: 15 / 15
• Subtask 3: 7 / 7
• Subtask 4: 29 / 29
• Subtask 5: 16 / 16
• Subtask 6: 25 / 25