Submission #391034

#	Time	Username	Problem	Language	Result	Execution time	Memory
391034		Victor	Railway (BOI17_railway)	C++17	100 / 100	973 ms	149480 KiB

railway

#include <bits/stdc++.h>

using namespace std;

#define rep(i, a, b) for (int i = a; i < (b); ++i)
#define per(i, a, b) for (int i = b - 1; i >= (a); --i)
#define trav(a, x) for (auto &a : x)

#define all(x) x.begin(), x.end()
#define sz(x) x.size()
#define pb push_back

#define umap unordered_map
#define uset unordered_set

typedef pair<int, int> ii;
typedef pair<int, ii> iii;
typedef vector<int> vi;
typedef vector<ii> vii;
typedef vector<vi> vvi;
typedef long long ll;

const int INF = 1000000007;

int n, m, k, cnt[100001], curr, jmp[100001][18], edgenum[100001], depth[100001];
vi ans, add[100001], rem[100001];
vii graph[100001];

void build(int u, int p, int d) {
    jmp[u][0] = p;
    depth[u] = d++;

    trav(edge, graph[u]) {
        int v, num;
        tie(v, num) = edge;
        if (v != p) {
            edgenum[v] = num;
            build(v, u, d);
        }
    }
}

int lca(int u, int v) {
    if (depth[v] < depth[u]) swap(u, v);
    per(i, 0, 18) if ((1 << i) <= depth[v] - depth[u]) {
        v = jmp[v][i];
    }

    if (u == v) return u;

    per(i, 0, 18) if (jmp[u][i] != jmp[v][i]) {
        u = jmp[u][i];
        v = jmp[v][i];
    }

    return jmp[u][0];
}

umap<int, bitset<100001>> mp;
vii vec;

int main() {
    cin.tie(0)->sync_with_stdio(0);
    cin.exceptions(cin.failbit);

    cin >> n >> m >> k;
    int a, b;

    rep(i, 0, n - 1) {
        cin >> a >> b;
        graph[--a].emplace_back(--b, i);
        graph[b].emplace_back(a, i);
    }

    build(0, 0, 0);
    rep(j, 1, 18) rep(i, 0, n) jmp[i][j] = jmp[jmp[i][j - 1]][j - 1];

    rep(i, 0, m) {
        int s, u, v;
        cin >> s >> u;
        add[--u].pb(i);
        rep(j, 1, s) {
            cin >> v;
            add[--v].pb(i);
            int cand = lca(u, v);
            if (depth[cand] < depth[u]) u = cand;
        }
        rem[u].pb(i);
    }

    rep(i, 1, n) vec.emplace_back(depth[i], i);
    sort(all(vec), greater<>());
    bitset<100001> bs;

    trav(neigh, vec) {
        int u = neigh.second;
        
        if (mp.count(u))
            bs = mp[u];
        else
            bs.reset();

        mp.erase(u);
        int p = jmp[u][0];
        trav(layer, add[u]) bs[layer] = 1;
        trav(layer, rem[u]) bs[layer] = 0;
        if (u && k <= (int)bs.count()) ans.pb(edgenum[u]);

        if (p) {
            if (mp.count(p))
                mp[p] |= bs;
            else
                mp.emplace(p, bs);
        }
    }
    
    sort(all(ans));
    cout << sz(ans) << endl;
    trav(edge, ans) cout << edge + 1 << ' ';
    cout << endl;
    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