Submission #1115836

#	Time	Username	Problem	Language	Result	Execution time	Memory
1115836		vjudge1	Railway (BOI17_railway)	C++17	100 / 100	92 ms	90312 KiB

railway

#include <bits/stdc++.h>
using namespace std;

#define name "TENBAI"
#define fi first
#define se second
#define int long long
#define endl '\n'
#define setmin(x, y) x = min((x), (y))
#define setmax(x, y) x = max((x), (y))
#define sqr(x) ((x) * (x))

mt19937 hdp(chrono::high_resolution_clock::now().time_since_epoch().count());
int rand(int l, int r){return l + ((hdp() % (r - l + 1)) + r - l + 1) % (r - l + 1);}

const int NM = 2e5 + 5;
const int LG = 20;

vector<int> ans;
vector<pair<int, int>> g[NM];
int n, m, k, tin[NM], tout[NM], dep[NM], timer, dp[NM];
pair<int, int> st[NM][LG], p[NM];

int lca(int u, int v)
{
    u = tin[u], v = tin[v];
    if (u > v)
        swap(u, v);
    int L = __lg(v - u + 1);
    return min(st[u][L], st[v - (1 << L) + 1][L]).se;
}

bool ancestor(int u, int v)
{
    return tin[u] <= tin[v] && tout[u] >= tout[v];
}

void upd(vector<int>& V)
{
    sort(V.begin(), V.end(), [&](const int& x, const int& y){return tin[x] < tin[y];});
    for (int j = V.size(), i = 1; i < j; i++)
        V.push_back(lca(V[i], V[i - 1]));
    sort(V.begin(), V.end(), [&](const int& x, const int& y){return tin[x] < tin[y];});
    V.erase(unique(V.begin(), V.end()), V.end());
    vector<int> st;
    for (int u : V)
    {
        while (st.size() && !ancestor(st.back(), u))
            st.pop_back();
        if (st.size())
            dp[st.back()]--, dp[u]++;
        st.push_back(u);
    }
}

void dfs(int u)
{
    st[++timer][0] = {dep[u], u};
    tin[u] = timer;
    for (auto v : g[u])
        if (v.fi != p[u].fi)
        {
            dep[v.fi] = dep[u] + 1;
            p[v.fi] = {u, v.se};
            dfs(v.fi);
            st[++timer][0] = {dep[u], u};
        }
    tout[u] = timer;
}

void DFS(int u)
{
    for (auto v : g[u])
        if (v.fi != p[u].fi)
        {
            DFS(v.fi);
            dp[u] += dp[v.fi];
        }
    if (u != 1 && dp[u] >= k)
        ans.push_back(p[u].se);
}

void solve()
{
    cin >> n >> m >> k;
    for (int i = 1; i < n; i++)
    {
        int u, v;
        cin >> u >> v;
        g[u].emplace_back(v, i);
        g[v].emplace_back(u, i);
    }
    dfs(1);
    for (int i = 1; (1 << i) <= timer; i++)
        for (int j = 1; j + (1 << i) - 1 <= timer; j++)
            st[j][i] = min(st[j][i - 1], st[j + (1 << i - 1)][i - 1]);
    while (m--)
    {
        int t;
        cin >> t;
        vector<int> V;
        while (t--)
        {
            int u;
            cin >> u;
            V.push_back(u);
        }
        upd(V);
    }
    DFS(1);
    sort(ans.begin(), ans.end());
    cout << ans.size() << endl;
    for (int t : ans)
        cout << t << ' ';
}

signed main()
{
    if (fopen("in.txt", "r")) 
    {
        freopen("in.txt", "r", stdin);
        freopen("out.txt", "w", stdout);
    }
    else if (fopen(name".inp", "r"))
    {
        freopen(name".inp", "r", stdin);
        freopen(name".out", "w", stdout);
    }
    ios_base::sync_with_stdio(false); cin.tie(nullptr); cout.tie(nullptr);
    int tc = 1; 
    // cin >> tc;
    while (tc--)
        solve();
}

Compilation message (stderr)

railway.cpp: In function 'void solve()':
railway.cpp:96:57: warning: suggest parentheses around '-' inside '<<' [-Wparentheses]
   96 |             st[j][i] = min(st[j][i - 1], st[j + (1 << i - 1)][i - 1]);
      |                                                       ~~^~~
railway.cpp: In function 'int main()':
railway.cpp:121:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  121 |         freopen("in.txt", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~
railway.cpp:122:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  122 |         freopen("out.txt", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
railway.cpp:126:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  126 |         freopen(name".inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
railway.cpp:127:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  127 |         freopen(name".out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

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