Submission #787516

#	Time	Username	Problem	Language	Result	Execution time	Memory
787516		mgl_diamond	Railway (BOI17_railway)	C++17	7 / 100	53 ms	26040 KiB

railway

#include <bits/stdc++.h>
using namespace std;
using ll = long long;
 
#define foru(i, l, r) for(int i=(l); i<=(r); ++i)
#define ford(i, l, r) for(int i=(l); i>=(r); --i)
#define fore(x, v) for(auto &x : v)
#define all(x) (x).begin(), (x).end()
#define sz(x) (int)(x).size()
#define fi first
#define se second
#define file "input"
 
void setIO() {
  ios::sync_with_stdio(0);
  cin.tie(0); cout.tie(0);
  if (fopen(file".in", "r")) {
    freopen(file".in", "r", stdin);
    freopen(file".out", "w", stdout);
  }
}

const int N = 1e5+5, LOG = 17;

int n, m, k, add[N], par[N];
vector<pair<int, int>> e;
vector<int> graph[N], ret;
int cnt, st[N], en[N], anc[N][LOG];

void prep(int u, int p) {
  st[u] = ++cnt;
  anc[u][0] = p;
  foru(i, 1, LOG-1) anc[u][i] = anc[anc[u][i-1]][i-1];
  fore(i, graph[u]) {
    int v = e[i].fi ^ e[i].se ^ u;
    if (v == p) continue;
    par[v] = i;
    prep(v, u);
  }
  en[u] = cnt;
}

bool isAnc(int u, int v) {
  return st[u] <= st[v] && st[v] <= en[u];
}

int lca(int u, int v) {
  if (isAnc(u, v)) return u;
  ford(j, LOG-1, 0) if (!isAnc(anc[u][j], v)) u = anc[u][j];
  return anc[u][0];
}

int dfs(int u, int p) {
  int sum = 0;
  fore(i, graph[u]) { 
    int v = e[i].fi ^ e[i].se ^ u;
    if (v == p) continue;
    int value = dfs(v, u) + add[i];
    if (value >= k) ret.push_back(i);
    sum += value;
  }
  return sum;
}

int main() {
  setIO();

  cin >> n >> m >> k;

  foru(i, 2, n) {
    int u, v;
    cin >> u >> v;
    graph[u].push_back(sz(e));
    graph[v].push_back(sz(e));
    e.emplace_back(u, v);
  }

  par[1] = n+1;
  en[0] = n+1;
  prep(1, 0);

  foru(i, 1, m) {
    int k; 
    cin >> k;

    vector<int> node;
    foru(j, 1, k) {
      int u;
      cin >> u;
      node.push_back(u);
    }

    sort(all(node), [&](int u, int v){
      return st[u] < st[v];
    });

    int lst = node[0];
    // cout << lst << "\n";
    foru(j, 1, k-1) {
      int cur = node[j];
      lst = lca(lst, cur);
      add[par[cur]] += 1;
      add[par[lst]] -= 1;
      // cout << cur << " " << lst << "\n";
      lst = cur;
    }
    // cout << "-----------\n";
  }

  dfs(1, 0);
  sort(all(ret));
  cout << sz(ret) << "\n";
  fore(x, ret) cout << x+1 << " ";
}

Compilation message (stderr)

railway.cpp: In function 'void setIO()':
railway.cpp:18:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   18 |     freopen(file".in", "r", stdin);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~
railway.cpp:19:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   19 |     freopen(file".out", "w", stdout);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

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