Submission #554095

#	Time	Username	Problem	Language	Result	Execution time	Memory
554095		d4xn	Combo (IOI18_combo)	C++17	30 / 100	40 ms	304 KiB

combo

#include "combo.h"

#pragma GCC optimize ("Ofast")
#include <bits/stdc++.h>
using namespace std;

#define pb push_back

string guess_sequence(int N) {
  string p;

  for (char i : {'A', 'B', 'X', 'Y'}) {
    p.pb(i);

    if (press(p)) {
      for (int j = 1; j < N; j++) {
        p.pb(i);
      }
      break;
    }

    p.pop_back();
  }

  vector<char> v;
  for (char i : {'A', 'B', 'X', 'Y'}) {
    if (p[0] == i) continue;
    v.pb(i);
  }

  int idx = 1;
  while (idx < N) {

    for (int j = 0; j < 3; j++) {
      int k = j + rand() % (3 - j);
      swap(v[j], v[k]);
    }

    for (int i = idx+1; i - idx + 1 <= idx && i < N; i++) {
        p[i] = v[rand() % 3];
    }

    for (char &i : v) {
      p[idx] = i;
      int x = press(p);
      if (x > idx) {
        idx = x;
        break;
      }
    }
  }

  return p;
}

• Subtask 1: 5 / 5
• Subtask 2: 25 / 95