Submission #797467

#	Time	Username	Problem	Language	Result	Execution time	Memory
797467		peijar	The short shank; Redemption (BOI21_prison)	C++17	100 / 100	544 ms	225324 KiB

prison

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

string to_string(string s) { return s; }
template <typename T> string to_string(T v) {
  bool first = true;
  string res = "[";
  for (const auto &x : v) {
    if (!first)
      res += ", ";
    first = false;
    res += to_string(x);
  }
  res += "]";
  return res;
}

void dbg_out() { cout << endl; }
template <typename Head, typename... Tail> void dbg_out(Head H, Tail... T) {
  cout << ' ' << to_string(H);
  dbg_out(T...);
}

#ifdef DEBUG
#define dbg(...) cout << "(" << #__VA_ARGS__ << "):", dbg_out(__VA_ARGS__)
#else
#define dbg(...)
#endif

signed main(void) {
  ios_base::sync_with_stdio(false);
  cin.tie(0);

  int nbPer, nbMatelas, T;
  cin >> nbPer >> nbMatelas >> T;

  vector<int> x(nbPer);
  for (int i = 0; i < nbPer; ++i) {
    cin >> x[i];
    x[i] -= i;
  }

  deque<pair<int, int>> candidats;
  candidats.emplace_back(-1e18, -1);
  vector<int> f(nbPer);
  for (int i = 0; i < nbPer; ++i) {
    while (candidats.back().first >= x[i])
      candidats.pop_back();
    candidats.emplace_back(x[i], i);
    auto it = lower_bound(candidats.begin(), candidats.end(),
                          pair<int, int>(T - i, 1e18));
    it--;
    f[i] = it->second;
  }
  dbg(f);

  vector<pair<int, int>> intervalles;
  int nbJamais = 0;
  for (int i = 0; i < nbPer; ++i) {
    if (f[i] == i)
      continue;
    if (f[i] == -1)
      nbJamais++;
    else
      intervalles.emplace_back(f[i], i);
  }

  sort(intervalles.begin(), intervalles.end(), [&](auto l, auto r) {
    if (l.first == r.first)
      return l.second > r.second;
    else
      return l.first < r.first;
  });

  int nbInt = intervalles.size();

  vector<int> stk;
  vector<int> par(nbInt);
  for (int i = 0; i < nbInt; ++i) {
    auto [l, r] = intervalles[i];
    while (!stk.empty() and intervalles[stk.back()].second < l)
      stk.pop_back();
    if (!stk.empty())
      par[i] = stk.back();
    else
      par[i] = -1;
    stk.push_back(i);
  }
  for (int i = 0; i < nbInt; ++i)
    dbg(i, intervalles[i].first, intervalles[i].second, par[i]);

  vector<int> depth(nbInt);
  for (int i = 0; i < nbInt; ++i) {
    if (par[i] != -1)
      depth[i] = 1 + depth[par[i]];
  }

  vector<pair<int, int>> deepest(nbInt);
  for (int i = nbInt - 1; i >= 0; --i) {
    deepest[i] = max(deepest[i], pair(depth[i], i));
    if (par[i] != -1)
      deepest[par[i]] = max(deepest[par[i]], deepest[i]);
  }

  vector<vector<int>> childs(nbInt);

  for (int i = 0; i < nbInt; ++i)
    if (par[i] != -1)
      childs[par[i]].push_back(i);

  priority_queue<pair<int, int>> pq;
  vector<bool> erased(nbInt);

  for (int i = 0; i < nbInt; ++i)
    if (par[i] == -1)
      pq.emplace(deepest[i]);

  int sol = nbPer - nbJamais;

  for (int it = 0; it < nbMatelas and !pq.empty(); ++it) {
    auto [cnt, u] = pq.top();
    pq.pop();
    sol -= cnt + 1;
    while (u != -1 and !erased[u]) {
      erased[u] = true;
      for (int v : childs[u])
        if (!erased[v])
          pq.emplace(deepest[v].first - depth[v], deepest[v].second);
      u = par[u];
    }
  }
  cout << sol << endl;
}

• Subtask 1: 15 / 15
• Subtask 2: 10 / 10
• Subtask 3: 20 / 20
• Subtask 4: 10 / 10
• Subtask 5: 25 / 25
• Subtask 6: 20 / 20