Submission #659903

#	Time	Username	Problem	Language	Result	Execution time	Memory
659903		peijar	Rarest Insects (IOI22_insects)	C++17	99.78 / 100	73 ms	428 KiB

insects

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

set<int> calcInter(set<int> &a, set<int> &b) {
  set<int> ret;
  for (int x : a)
    if (b.count(x))
      ret.insert(x);
  return ret;
}

int min_cardinality(int N) {
  vector<int> roots;
  int nbCC = 0;
  for (int i = 0; i < N; ++i) {
    move_inside(i);
    if (i and press_button() == 2)
      move_outside(i);
    else
      roots.push_back(i), nbCC++;
  }
  vector<bool> isRoot(N);
  for (int r : roots)
    isRoot[r] = true;
  vector<int> toProcess;
  for (int i = 0; i < N; ++i)
    if (!isRoot[i])
      toProcess.push_back(i);
  if (nbCC == 1)
    return N;

  for (int r : roots) {
    move_outside(r);
    toProcess.push_back(r);
  }

  int lo = 1, up = N / nbCC;
  // invariant : everything outside of toProcess has majority element <= lo
  // We never need to reconsider insects !!
  int toAdd = 0;
  while (lo < up) {
    int mid = (lo + up + 1) / 2;
    vector<int> popped;
    vector<int> insideMachine;
    for (int u : toProcess) {
      move_inside(u);
      if (press_button() > mid)
        popped.push_back(u), move_outside(u);
      else
        insideMachine.push_back(u);
    }
    if ((int)popped.size() == N - mid * nbCC) {
      for (int u : insideMachine)
        move_outside(u);
      toProcess = popped;
      N = popped.size();
      toAdd += mid;
      lo = 0, up = min(N / nbCC, up - mid);
    } else {
      for (int u : insideMachine)
        move_outside(u);
      toProcess = insideMachine;
      N = toProcess.size();
      up = mid - 1;
    }
  }
  return lo + toAdd;
}

• Subtask 1: 10 / 10
• Subtask 2: 15 / 15
• Subtask 3: 74.78 / 75