Submission #876323

#	Time	Username	Problem	Language	Result	Execution time	Memory
876323		Kanon	Counting Mushrooms (IOI20_mushrooms)	C++14	88.28 / 100	5 ms	804 KiB

mushrooms

#include <bits/stdc++.h>
#include "mushrooms.h"
 
using namespace std;
 
 
const int magic = 84;
const int bound = 226;
 
mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
// generate random number between l, r : uniform_int_distribution<long long>(l, r)(rng)
// random shuffle : shuffle(.begin(), .end(), rng)
 
int count_mushrooms(int n) {
 
  if (n <= bound + 1) {
    int ret = 1;
    for (int i = 1; i < n; i++) {
      ret += use_machine({0, i}) ^ 1;
    }
    return ret;
  }
 
  vector<int> a(n, -1);
  a[0] = 0;
 
  vector<int> order(magic);
  iota(order.begin(), order.end(), 1);
  shuffle(order.begin(), order.end(), rng);
 
  int cnt = magic + 1;
  int iter = 1;
  map<int, vector<int>> best_choice;
 
  while (iter--) {
 
    order.insert(order.begin(), 0);
    order.push_back(cnt++);
    int st = use_machine(order);
    a[cnt - 1] = a[0] ^ (st & 1);
 
    best_choice[st] = order;
 
    int sz = order.size() / (st + 1);
    vector<int> Lorder, Rorder;
 
    for (int i = 1; i < (int) order.size() - 1; i++) {
      int md = i % (2 * sz);
      if (md >= sz) Rorder.push_back(order[i]);
      else Lorder.push_back(order[i]);
    }
 
    shuffle(Lorder.begin(), Lorder.end(), rng);
    shuffle(Rorder.begin(), Rorder.end(), rng);
    order = Lorder;
    order.insert(order.end(), Rorder.begin(), Rorder.end());
 
  }
 
  int st = best_choice.begin()->first;
  order = best_choice.begin()->second;
  vector<int> ONE, ZERO;
  ZERO.push_back(0);
  for (int i = 0; i < 2; i++) {
    a[cnt] = (use_machine({0, cnt}) & 1) ^ a[0];
    cnt++;
    if (a[cnt - 1] == 0) ZERO.push_back(cnt - 1);
    else ONE.push_back(cnt - 1);
  }
 
  function<void(int, int, int, vector<int>)> dfs = [&](int vL, int vR, int tot, vector<int> p) {
 
    assert(vL != -1 && vR != -1 && vL == a[p[0]] && vR == a[p.back()]);
    assert(0 <= tot && tot <= (int) p.size() - 1);
 
    if (p.size() <= 2) return;
    if (tot == 0) {
      for (int i = 1; i < (int) p.size() - 1; i++) a[p[i]] = a[p[i - 1]];
      return;
    }
    if (tot == (int) p.size() - 1) {
      for (int i = 1; i < (int) p.size() - 1; i++) a[p[i]] = a[p[i - 1]] ^ 1;
      return;
    }
 
    int sz = p.size();
    int mid = (sz + 1) / 2;
    assert(mid > 1);
 
    if (mid > 2) {
 
      vector<int> que(p.begin(), p.begin() + mid);
      que.push_back(cnt++);
 
      int st = use_machine(que);
      a[cnt - 1] = vL ^ (st & 1);
 
      dfs(vL, a[cnt - 1], st, que);
 
      for (int i = 1; i < mid; i++) {
        int u = que[i], v = que[i - 1];
        tot -= a[u] ^ a[v];
      }
 
    } else {
 
      vector<int> pii = ONE.size() >= 2 ? ONE : ZERO;
 
      int st = use_machine({pii[0], p[mid - 1], pii[1], cnt++});
 
      a[cnt - 1] = a[pii[0]] ^ (st & 1);
      st -= a[pii[1]] ^ a[cnt - 1];
 
      if (st > 0) a[p[mid - 1]] = a[pii[0]] ^ 1;
      else a[p[mid - 1]] = a[pii[0]];
 
      tot -= a[p[mid - 1]] ^ a[p[0]];
 
    }
 
    vector<int> que = vector<int>(p.begin() + mid - 1, p.end());
    dfs(a[p[mid - 1]], vR, tot, que);
 
  };
 
  dfs(a[0], a[order.back()], st, order);
 
  int ret = 0;
  vector<int> zeros, ones;
  for (int i = 0; i < cnt; i++) {
    if (a[i] == 0) zeros.push_back(i);
    else ones.push_back(i);
  }
  ret += zeros.size();
 
  while (cnt < n) {
 
    int len = min(n - cnt, (int) max(zeros.size(), ones.size()));
    vector<int> ids = zeros.size() >= ones.size() ? zeros : ones;
 
    vector<int> que;
    for (int i = 0; i < len; i++) {
      que.push_back(ids[i]);
      que.push_back(cnt++);
    }
 
    int st = use_machine(que);
 
    if (ids == ones) {
 
      a[cnt - 1] = 1 ^ (st & 1);
      ret += a[cnt - 1] == 0;
      st -= a[cnt - 1] == 0;
 
      if (a[cnt - 1] == 0) zeros.push_back(cnt - 1);
      else ones.push_back(cnt - 1);
 
      assert(st % 2 == 0);
      ret += st >> 1;
 
    } else {
 
      a[cnt - 1] = 0 ^ (st & 1);
      ret += a[cnt - 1] == 0;
      st -= a[cnt - 1] == 1;
 
      if (a[cnt - 1] == 0) zeros.push_back(cnt - 1);
      else ones.push_back(cnt - 1);
 
      assert(st % 2 == 0);
      ret += (len - 1) - (st >> 1);
 
    }
  }
  return ret;
}
 

• Subtask 1: 88.2812 / 100