Submission #865084

#	Time	Username	Problem	Language	Result	Execution time	Memory
865084		overwatch9	Railway (BOI17_railway)	C++17	100 / 100	186 ms	30420 KiB

railway

#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
vector <vector <pair <int, int>>> adj;
vector <vector <int>> anc;
vector <int> visit, finish, parent_edge;
vector <pair <int, int>> edges;
int t = 0;
void dfs(int s, int p) {
    visit[s] = t++;
    anc[s][0] = p;
    for (int i = 1; i < 20; i++)
        anc[s][i] = anc[anc[s][i-1]][i-1];
    for (auto i : adj[s]) {
        if (i.first == p)
            continue;
        parent_edge[i.first] = i.second;
        dfs(i.first, s);
    }
    finish[s] = t++;
}
bool is_ancestor(int a, int b) {
    return visit[a] <= visit[b] && finish[a] >= finish[b];
}
int get_lca(int a, int b) {
    if (is_ancestor(a, b))
        return a;
    if (is_ancestor(b, a))
        return b;
    int lca = a;
    for (int i = 19; i >= 0; i--) {
        if (!is_ancestor(anc[lca][i], b))
            lca = anc[lca][i];
    }
    return anc[lca][0];
}
bool comp(int a, int b) {
    return visit[a] < visit[b];
}
struct stree {
    #define lc v*2
    #define rc v*2+1
    vector <int> tree;
    stree (int s) {
        tree.resize(s*4);
    }
    void pushup(int v) {
        tree[v] = tree[lc] + tree[rc];
    }
    void update(int v, int tl, int tr, int p, int val) {
        if (tl > p || tr < p)
            return;
        if (tl == tr) {
            tree[v] += val;
            return;
        }
        int tm = (tl + tr) / 2;
        update(lc, tl, tm, p, val);
        update(rc, tm+1, tr, p, val);
        pushup(v);
    }
    int query(int v, int tl, int tr, int l, int r) {
        if (tl > r || tr < l)
            return 0;
        if (tl >= l && tr <= r)
            return tree[v];
        int tm = (tl + tr) / 2;
        int a = query(lc, tl, tm, l, r);
        int b = query(rc, tm+1, tr, l, r);
        return a + b;
    }
};
int main() {
    // freopen("in.txt", "r", stdin);
    // freopen("out.txt", "w", stdout);
    int n, m, k;
    cin >> n >> m >> k;
    adj.resize(n+1);
    parent_edge = visit = finish = vector <int> (n+1);
    anc = vector <vector <int>> (n+1, vector <int> (20));
    edges.resize(n+1);
    for (int i = 1; i < n; i++) {
        int a, b;
        cin >> a >> b;
        edges[i] = {a, b};
        adj[a].push_back({b, i});
        adj[b].push_back({a, i});
    }
    dfs(1, 1);
    stree tree(t+1);
    for (int i = 0; i < m; i++) {
        int f;
        cin >> f;
        vector <int> chosen(f);
        for (int j = 0; j < f; j++)
            cin >> chosen[j];
        sort(chosen.begin(), chosen.end(), comp);
        chosen.push_back(chosen[0]);
        for (int j = 0; j < f; j++) {
            int a = chosen[j], b = chosen[j+1];
            int lca = get_lca(a, b);
            tree.update(1, 0, t, visit[a], 1);
            tree.update(1, 0, t, visit[b], 1);
            tree.update(1, 0, t, visit[lca], -2);
        }
    }
    vector <int> approved;
    for (int i = 1; i <= n; i++) {
        int res = tree.query(1, 0, t, visit[i], finish[i]);
        if (res >= 2*k) {
            int edge_id = parent_edge[i];
            if (edge_id != 0)
                approved.push_back(edge_id);
        }
    }
    sort(approved.begin(), approved.end());
    cout << approved.size() << '\n';
    for (auto i : approved)
        cout << i << ' ';
    cout << '\n';
}

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