Submission #1096149

#	Time	Username	Problem	Language	Result	Execution time	Memory
1096149		TrinhKhanhDung	Railway (BOI17_railway)	C++14	100 / 100	64 ms	25288 KiB

railway

#include <bits/stdc++.h>
#define ll long long
#define fi first
#define se second
#define sz(x) (int)x.size()
#define ALL(v) v.begin(),v.end()
#define MASK(k) (1LL << (k))
#define BIT(x, i) (((x) >> (i)) & 1)
#define oo (ll)1e18 + 10
#define INF (ll)1e9
#define MOD (ll)(998244353)

using namespace std;

template<class T1, class T2>
    bool maximize(T1 &a, T2 b){if(a < b){a = b; return true;} return false;}

template<class T1, class T2>
    bool minimize(T1 &a, T2 b){if(a > b){a = b; return true;} return false;}

template<class T1, class T2>
    void add(T1 &a, T2 b){a += b; if(a >= MOD) a -= MOD;}

template<class T1, class T2>
    void sub(T1 &a, T2 b){a -= b; if(a < 0) a += MOD;}

template<class T>
    void cps(T &v){sort(ALL(v)); v.resize(unique(ALL(v)) - v.begin());}

const int maxN = 1e5 + 10, LOG = 17;

int N, M, K;
vector<pair<int, int>> adj[maxN];
int idEdge[maxN], in[maxN], out[maxN], timer, h[maxN], d[maxN][LOG], cnt[maxN];

void dfs(int u, int p = -1){
    in[u] = ++timer;
    for(auto o: adj[u]){
        int v = o.fi, id = o.se;
        if(v == p) continue;

        h[v] = h[u] + 1;
        d[v][0] = u;
        for(int i = 1; i < LOG; i++){
            d[v][i] = d[d[v][i - 1]][i - 1];
        }
        idEdge[v] = id;

        dfs(v, u);
    }
    out[u] = timer;
}

int lca(int u, int v){
    if(h[u] < h[v]) swap(u, v);
    int delta = h[u] - h[v];
    for(int i = 0; i < LOG; i++) if(BIT(delta, i)){
        u = d[u][i];
    }
    if(u == v) return u;
    for(int i = LOG - 1; i >= 0; i--) if(d[u][i] != d[v][i]){
        u = d[u][i];
        v = d[v][i];
    }
    return d[u][0];
}

void solve(){
    cin >> N >> M >> K;
    for(int i = 1; i < N; i++){
        int u, v; cin >> u >> v;
        adj[u].push_back({v, i});
        adj[v].push_back({u, i});
    }

    dfs(1);

    for(int p = 1; p <= M; p++){
        int k; cin >> k;
        vector<int> index;
        for(int i = 1; i <= k; i++){
            int x; cin >> x;
            index.push_back(x);
        }
        sort(ALL(index), [&](int u, int v){return in[u] < in[v];});
        for(int i = 1; i < k; i++){
            index.push_back(lca(index[i], index[i - 1]));
        }
        cps(index);
        sort(ALL(index), [&](int u, int v){return in[u] < in[v];});

        stack<int> st;
        for(int x: index){
            while(sz(st) && in[x] > out[st.top()]) st.pop();
            if(sz(st)){
                int y = st.top();
                cnt[in[x]]++;
                cnt[in[y]]--;
            }
            st.push(x);
        }
    }

    for(int i = 1; i <= N; i++) cnt[i] += cnt[i - 1];
//    cout << '\n';
    vector<int> ans;
    for(int i = 2; i <= N; i++){
        if(cnt[out[i]] - cnt[in[i] - 1] >= K) ans.push_back(idEdge[i]);
    }

    sort(ALL(ans));

    cout << sz(ans) << '\n';
    for(int x: ans) cout << x << ' ';
}

int main(){
    ios_base::sync_with_stdio(0); cin.tie(0);
//    freopen("task.inp","r",stdin);
//    freopen("task.out","w",stdout);

    int T = 1;
//    cin >> T;
    for(; T > 0; T--) solve();

    return 0;
}

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