Submission #823758

#	Time	Username	Problem	Language	Result	Execution time	Memory
823758		arush_agu	Railway (BOI17_railway)	C++17	36 / 100	74 ms	60572 KiB

railway

#include <algorithm>
#include <cctype>
#include <cmath>
#include <cstdio>
#include <cstring>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#include <functional>
#include <iomanip>
#include <iostream>
#include <iterator>
#include <list>
#include <map>
#include <numeric>
#include <queue>
#include <random>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <vector>

#ifdef DEBUG
#include <time.h>
#endif

#define all(a) (a).begin(), (a).end()
#define rev(a) (a).rbegin(), (a).rend()
#define F first
#define S second
int recur_depth = 0;
#ifdef DEBUG
#define dbg(x)                                                                 \
  {                                                                            \
    ++recur_depth;                                                             \
    auto x_ = x;                                                               \
    --recur_depth;                                                             \
    cerr << string(recur_depth, '\t') << "\e[91m" << __func__ << ":"           \
         << __LINE__ << "\t" << #x << " = " << x_ << "\e[39m" << endl;         \
  }
#else
#define dbg(x)
#endif

using namespace std;
using namespace __gnu_pbds;

typedef pair<int, int> ii;

typedef long long ll;
typedef long double ld;
typedef pair<ll, ll> llll;

typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<pair<int, int>> vii;
typedef vector<vii> vvii;

typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef vector<pair<ll, ll>> vll;
typedef vector<vll> vvll;

typedef vector<bool> vb;

template <class type1>
using ordered_set = tree<type1, null_type, less<type1>, rb_tree_tag,
                         tree_order_statistics_node_update>;

template <typename A, typename B>
ostream &operator<<(ostream &os, const pair<A, B> &p) {
  return os << '(' << p.first << ", " << p.second << ')';
}
template <typename T_container, typename T = typename enable_if<
                                    !is_same<T_container, string>::value,
                                    typename T_container::value_type>::type>
ostream &operator<<(ostream &os, const T_container &v) {
  os << '{';
  string sep;
  for (const T &x : v)
    os << sep << x, sep = ", ";
  return os << '}';
}

const ll MOD = 1e9 + 7;
// const ll MOD = 998244353;
const ll INF = 1e9;
const ld EPS = 1e-9;

struct Edge {
  int u, v, idx;
  int cnt_req;

  Edge(int u, int v, int idx) : u(u), v(v), idx(idx) {}
};

struct ST {
  const int MAXLG = 22;
  int n;
  vi lg2;
  vvii st;

  ST(vii &a) : n(a.size()) {
    st = vvii(MAXLG, vii(n));
    st[0] = a;
    for (int j = 1; j < MAXLG; j++)
      for (int i = 0; i + (1 << j) <= n; i++)
        st[j][i] = min(st[j - 1][i], st[j - 1][i + (1 << (j - 1))]);

    lg2 = vi(n + 1);
    lg2[1] = 0;
    for (int i = 2; i <= n; i++)
      lg2[i] = lg2[i / 2] + 1;
  }

  int query(int l, int r) {
    if (l > r)
      swap(l, r);
    int k = lg2[r - l + 1];
    return min(st[k][l], st[k][r - (1 << k) + 1]).second;
  }
};

void solve() {
  int n, m, k;
  cin >> n >> m >> k;
  vvii adj(n);
  vector<Edge> eds;
  for (int i = 0; i < n - 1; i++) {
    int u, v;
    cin >> u >> v;
    u--, v--;
    adj[u].push_back({v, i});
    adj[v].push_back({u, i});
    eds.push_back(Edge(u, v, i));
  }

  int timer = 0;
  vi depth(n), first_occ(n);
  vii par(n, {-1, -1}), euler;
  function<void(int, int)> f = [&](int u, int p) {
    first_occ[u] = euler.size();
    euler.push_back({depth[u], u});

    for (auto [v, i] : adj[u])
      if (v != p) {
        depth[v] = depth[u] + 1;
        par[v] = {u, i};
        f(v, u);
        euler.push_back({depth[u], u});
      }
  };
  f(0, -1);

  ST st(euler);

  vi cnt(n);
  for (int i = 0; i < m; i++) {
    int s;
    cin >> s;
    vi us(s);
    for (int &x : us)
      cin >> x, x--;

    int lca = st.query(first_occ[us[0]], first_occ[us[1]]);
    cnt[us[0]]++, cnt[us[1]]++;
    cnt[lca] -= 2;
    for (int i = 2; i < s; i++) {
      int u = us[i];
      cnt[u]++;

      int nxt_lca = st.query(first_occ[u], first_occ[lca]);

      if (lca != nxt_lca) {
        cnt[lca = nxt_lca]--;
        continue;
      }

      cnt[st.query(first_occ[u], first_occ[us[i - 1]])]--;
    }
  }

  function<void(int, int)> g = [&](int u, int p) {
    for (auto [v, i] : adj[u])
      if (v != p) {
        g(v, u);
        cnt[u] += cnt[v];
      }
  };
  g(0, -1);

  assert(cnt[0] == 0);
  for (int i = 1; i < n; i++) {
    eds[par[i].second].cnt_req = cnt[i];
  }

  vi res;
  for (int i = 0; i < n - 1; i++)
    if (eds[i].cnt_req >= k)
      res.push_back(i);

  cout << res.size() << "\n";
  for (int &x : res)
    cout << x + 1 << " ";
  cout << "\n";
}

int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(NULL);

  clock_t start = clock();

  int test_cases = 1;
  // cin >> test_cases;

  while (test_cases--)
    solve();

#ifdef DEBUG
  cerr << fixed << setprecision(10)
       << "\nTime Taken: " << (double)(clock() - start) / CLOCKS_PER_SEC
       << "s\n";
#endif
  return 0;
}

Compilation message (stderr)

railway.cpp: In function 'void solve()':
railway.cpp:140:7: warning: unused variable 'timer' [-Wunused-variable]
  140 |   int timer = 0;
      |       ^~~~~
railway.cpp: In function 'int main()':
railway.cpp:214:11: warning: unused variable 'start' [-Wunused-variable]
  214 |   clock_t start = clock();
      |           ^~~~~

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