Submission #708306

#	Time	Username	Problem	Language	Result	Execution time	Memory
708306		_martynas	Railway (BOI17_railway)	C++11	100 / 100	113 ms	26480 KiB

railway

#include <bits/stdc++.h>

using namespace std;

using ll = long long;
using pii = pair<int, int>;
using pli = pair<ll, int>;
using pll = pair<ll, ll>;
using vi = vector<int>;
using vl = vector<ll>;

const int MOD = 1e9+7;

#define F first
#define S second
#define PB push_back
#define all(a) (a).begin(), (a).end()
#define rall(a) (a).rbegin(), (a).rend()

void FASTIO() {ios::sync_with_stdio(0); cin.tie(0); cout.tie(0); }

const int MXN = 1e5+5;

int n, m, k;
vector<pii> adj[MXN];
int order[MXN]; int counter = 0;
int H[MXN], lift[18][MXN];
int A[MXN];
vi ans;

void postorder(int u, int p) {
    for(auto e : adj[u]) if(e.F != p) {
        postorder(e.F, u);
    }
    order[u] = counter++;
}

void build_lift(int u, int p) {
    H[u] = H[p]+1;
    lift[0][u] = p;
    for(auto e : adj[u]) if(e.F != p) {
        build_lift(e.F, u);
    }
}

int get_lca(int a, int b) {
    if(H[a] < H[b]) swap(a, b);
    // lift a to match b height
    for(int p = 17; p >= 0; p--)
    while(H[a]-(1<<p) >= H[b]) {
        a = lift[p][a];
    }
    if(a == b) return a;
    for(int p = 17; p >= 0; p--) {
        while(lift[p][a] != lift[p][b]) {
            a = lift[p][a];
            b = lift[p][b];
        }
    }
    return lift[0][a];
}

int dfs(int u, int p) {
    int sum = A[u];
    for(auto e : adj[u]) if(e.F != p) {
        int subtree = dfs(e.F, u);
        if(subtree >= k) {
            ans.PB(e.S);
        }
        sum += subtree;
    }
    return sum;
}

int main() {
    FASTIO();
    cin >> n >> m >> k;
    for(int i = 1; i < n; i++) {
        int a, b; cin >> a >> b;
        adj[a].PB({b, i});
        adj[b].PB({a, i});
    }
    postorder(1, 1);
    build_lift(1, 1);
    for(int p = 1; p < 18; p++) {
        for(int i = 1; i <= n; i++) {
            lift[p][i] = lift[p-1][lift[p-1][i]];
        }
    }
    for(int i = 0; i < m; i++) {
        int sz; cin >> sz;
        vi comp(sz);
        for(int j = 0; j < sz; j++) cin >> comp[j];
        sort(all(comp), [&](int a, int b) {
             return order[a] < order[b];
        });
        for(int j = 0; j < sz; j++) A[comp[j]]++;
        for(int j = 0; j < sz; j++) {
            int lca = get_lca(comp[j], comp[(j+1)%sz]);
            A[lca]--;
        }
    }
    dfs(1, -1);
    sort(all(ans));
    cout << ans.size() << "\n";
    for(int x : ans) cout << x << " ";
    cout << "\n";
    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