Submission #566372

#	Time	Username	Problem	Language	Result	Execution time	Memory
566372		lorenzoferrari	The Big Prize (IOI17_prize)	C++17	97.60 / 100	80 ms	848 KiB

prize

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

int mx_cnt;
int answer = -1;
map<int, array<int, 2>> memo;
map<int, set<int>> found;

array<int, 2> askme(int i) {
  array<int, 2> ans;
  if (memo.find(i) != memo.end()) {
    ans[0] = memo[i][0];
    ans[1] = memo[i][1];
  } else {
    auto v = ask(i);
    ans[0] = v[0];
    ans[1] = v[1];
  }
  memo[i] = {ans[0], ans[1]};
  found[ans[0] + ans[1]].insert(i);
  if (ans[0] + ans[1] == 0) answer = i;
  return ans;
}
int count(int i) { return askme(i)[0] + askme(i)[1]; }

bool makes_sense(int l, int r) {
  for (auto& ss : found) {
    if (ss.first == mx_cnt) continue;
    auto& s = ss.second;
    auto il = s.lower_bound(l);
    auto ir = s.lower_bound(r);
    if (il == s.begin()) continue;
    if (ir == s.end()) continue;
    il = prev(il);
    if (askme(*ir)[0] - askme(*il)[0] == 0) return false;
  }
  return true;
}

void findall(int l, int r) {
  for (; count(l) != mx_cnt; ++l) if (answer != -1) return;
  for (; count(r) != mx_cnt; --r) if (answer != -1) return;
  if (!makes_sense(l, r)) return;
  if (l >= r) return;
  int cnt = askme(r)[0] - askme(l)[0];
  if (cnt <= 0) return;
  if (answer != -1) return;
  int m = (l + r) / 2;
  findall(l, m);
  findall(m, r);
}

int find_best(int n) {
  srand(time(NULL));
  for (int i = 0; i < 500; ++i) mx_cnt = max(mx_cnt, count(rand() % n));
  int l = 0; while (count(l) != mx_cnt) ++l;
  int r = n-1; while (count(r) != mx_cnt) --r;
  findall(l, r);
  return answer;
}

#ifdef LORENZO
int main() {
  cout << "insert n: "; fflush(stdout);
  int n; cin >> n;
  cout << "answer: " << find_best(n) << endl;
}
#endif

• Subtask 1: 20 / 20
• Subtask 2: 77.6 / 80