Submission #1099135

#	Time	Username	Problem	Language	Result	Execution time	Memory
1099135		LeDaiKing	Railway (BOI17_railway)	C++14	29 / 100	65 ms	26144 KiB

railway

#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define fi first
#define se second
#define pb push_back
#define ALL(n) n.begin(), n.end()
#define mask(n) (1ll << (n))
#define ck(n, k) (((n) >> (k))&1)
#define LOG 17
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

int f[100005], dfsnum[100005], lca[100005][20], hight[100005];
pair<int, int> edges[100005];
vector<int> adj[100005];
int num = 0;

void dfs(int pa, int u)
{
    // cout << pa << " " << u << endl;
    lca[u][0] = pa;
    hight[u] = hight[pa] + 1;

    for (auto v : adj[u]) if (v != pa)
    {
        dfs(u, v);
    }

    dfsnum[u] = ++num;
}

void preprocessLCA(int n)
{
    dfs(0, 1);
    for (int j = 1; j <= LOG; j++)
    for (int i = 1; i <= n; i++)
    lca[i][j] = lca[lca[i][j - 1]][j - 1];
}

int getLCA(int u, int v)
{
    if (hight[u] < hight[v]) return getLCA(v, u);

    for (int i = LOG; i >= 0; i--) if (hight[lca[u][i]] >= hight[v]) u = lca[u][i];

    if (u == v) return u;

    for (int i = LOG; i >= 0; i--) if (lca[u][i] != lca[v][i])
    {
        u = lca[u][i]; v = lca[v][i];
    }

    return lca[u][0];
}

void dfs1(int pa, int u)
{
    for (auto v : adj[u]) if (v != pa)
    {
        dfs1(u, v); 
        f[u] += f[v];
    }
}

void solution()
{
    int n, m, k;
    cin >> n >> m >> k;

    for (int i = 1; i < n; i++)
    {
        int x, y;
        cin >> x >> y;
        adj[x].pb(y);
        adj[y].pb(x);
        edges[i] = {x, y};
    }

    preprocessLCA(n);

    while(m--)
    {
        int num;
        cin >> num;
        vector<int> ldk(num);
        for (int i = 0; i < num; i++) cin >> ldk[i];

        sort(ALL(ldk), [&](const int &x, const int &y)
        {
            return dfsnum[x] < dfsnum[y];
        });

        
        for (int i = 1; i < (int)ldk.size(); i++)
        {
            int par = getLCA(ldk[i - 1], ldk[i]);

            f[ldk[i]]++; f[par]--;
            if (i == 1)
            {
                f[ldk[0]]++; f[par]--;
            }
        }
    }

    dfs1(0, 1);

    vector<int> ans;

    for (int i = 1; i < n; i++)
    {
        if (hight[edges[i].fi] < hight[edges[i].se]) swap(edges[i].fi, edges[i].se);
        if (f[edges[i].fi] >= k)
        {
            ans.pb(i);
        }
    }

    cout << (int)ans.size() << "\n";

    for (auto v : ans) cout << v << " ";
}

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

    solution();
}

• Subtask 1: 0 / 8
• Subtask 2: 0 / 15
• Subtask 3: 0 / 7
• Subtask 4: 29 / 29
• Subtask 5: 0 / 16
• Subtask 6: 0 / 25