Submission #890459

#	Time	Username	Problem	Language	Result	Execution time	Memory
890459		zeta7532	Railway (BOI17_railway)	C++17	100 / 100	156 ms	38728 KiB

railway

#include <bits/stdc++.h>
#pragma GCC target("avx2")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
using namespace std;
using ll = long long;
const ll mod = 998244353;
#define fi first
#define se second
#define rep(i,n) for(ll i=0;i<n;i++)
#define all(x) x.begin(),x.end()
#define faster ios::sync_with_stdio(false);cin.tie(nullptr)

using Graph = vector<vector<ll>>;

struct LCA{
    vector<vector<ll>> par;
    vector<ll> dis;
    LCA(const Graph &G,ll root=0){init (G,root);}
    void init(const Graph &G,ll root=0){
        ll v=G.size();
        ll k=1;
        while((1<<k)<v) k++;
        par.assign(k,vector<ll>(v,-1));
        dis.assign(v,-1);
        dfs(G,root,-1,0);
        for(ll i=0;i+1<k;i++){
            for(ll j=0;j<v;j++){
                if(par[i][j]<0) par[i+1][j]=-1;
                else par[i+1][j]=par[i][par[i][j]];
            }
        }
    }
    void dfs(const Graph &G,ll v,ll p,ll d){
        par[0][v]=p;
        dis[v]=d;
        for(ll nv:G[v]){
            if(nv!=p) dfs(G,nv,v,d+1);
        }
    }
    ll query(ll u,ll v){
        if(dis[u]<dis[v]) swap(u,v);
        ll K=par.size();
        for(ll k=0;k<K;k++){
            if((dis[u]-dis[v])>>k&1){
                u=par[k][u];
            }
        }
        if(u==v) return u;
        for(ll k=K-1;k>=0;k--){
            if(par[k][u]!=par[k][v]){
                u=par[k][u];
                v=par[k][v];
            }
        }
        return par[0][u];
    }
    ll get_dis(ll u,ll v){return dis[u]+dis[v]-2*dis[query(u,v)];}
};

vector<ll> bfs(vector<vector<ll>> G){
    ll N=G.size();
    vector<ll> dis(N,-1);
    dis[0]=0;
    queue<ll> que;
    que.push(0);
    while(!que.empty()){
        ll v=que.front();
        que.pop();
        for(ll nv:G[v]){
            if(dis[nv]!=-1) continue;
            dis[nv]=dis[v]+1;
            que.push(nv);
        }
    }
    return dis;
}

int main() {
    ll N,Q,K;
    cin >> N >> Q >> K;
    vector<ll> A(N-1),B(N-1);
    Graph G(N);
    rep(i,N-1){
        cin >> A[i] >> B[i];
        A[i]--,B[i]--;
        G[A[i]].push_back(B[i]);
        G[B[i]].push_back(A[i]);
    }
    vector<ll> dis=bfs(G);
    vector<ll> Eid(N,-1);
    rep(i,N-1){
        if(dis[A[i]]>dis[B[i]]) Eid[A[i]]=i;
        if(dis[B[i]]>dis[A[i]]) Eid[B[i]]=i;
    }
    ll cnt=0;
    vector<ll> Vid(N);
    function<void(ll)> dfs=[&](ll v){
        Vid[v]=cnt;
        cnt++;
        for(ll nv:G[v]){
            if(dis[nv]<dis[v]) continue;
            dfs(nv);
        }
    };
    dfs(0);
    vector<ll> imos(N,0);
    LCA ans(G);
    while(Q--){
        ll M;
        cin >> M;
        vector<pair<ll,ll>> P(M);
        rep(i,M){
            ll v;
            cin >> v;
            v--;
            P[i].fi=Vid[v];
            P[i].se=v;
        }
        sort(all(P));
        rep(i,M){
            ll x=P[i].se;
            ll y=P[(i+1)%M].se;
            ll z=ans.query(x,y);
            imos[x]+=1;
            imos[y]+=1;
            imos[z]-=2;
        }
    }
    function<void(ll)> sum=[&](ll v){
        ll par=-1;
        for(ll nv:G[v]){
            if(dis[nv]<dis[v]){
                par=nv;
                continue;
            }
            sum(nv);
        }
        if(par>=0) imos[par]+=imos[v];
    };
    sum(0);
    vector<ll> ANS;
    rep(i,N){
        if(imos[i]>=K*2) ANS.push_back(Eid[i]+1);
    }
    sort(all(ANS));
    cout << ANS.size() << endl;
    rep(i,ANS.size()){
        cout << ANS[i] << " ";
    }
    cout << endl;
    return 0;
}

Compilation message (stderr)

railway.cpp: In function 'int main()':
railway.cpp:10:30: warning: comparison of integer expressions of different signedness: 'll' {aka 'long long int'} and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   10 | #define rep(i,n) for(ll i=0;i<n;i++)
......
  148 |     rep(i,ANS.size()){
      |         ~~~~~~~~~~~~          
railway.cpp:148:5: note: in expansion of macro 'rep'
  148 |     rep(i,ANS.size()){
      |     ^~~

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