Submission #69346

#	Time	Username	Problem	Language	Result	Execution time	Memory
69346		Noam527	The Big Prize (IOI17_prize)	C++17	97.02 / 100	83 ms	1152 KiB

prize

#include "prize.h"
#include <bits/stdc++.h>
#define endl '\n'
#define fast ios::sync_with_stdio(0), cin.tie(0), cout.tie(0)
#define debug cout << "ok" << endl
#define finish(x) return cout << x << endl, 0
typedef long long ll;
typedef long double ldb;
const int md = 1e9 + 7, inf = 1e9 + 7;
const ll hs = 199;
const ldb eps = 1e-9, pi = acos(-1);
using namespace std;
/*
vector<int> ask(int i) {
	cout << "? " << i << endl;
	vector<int> rtn(2);
	cin >> rtn[0] >> rtn[1];
	return rtn;
}
*/

map<int, vector<int>> alreadyfound;
vector<int> Q(int i) {
	if (alreadyfound.count(i)) return alreadyfound[i];
	return alreadyfound[i] = ask(i);
}

int N, badval;

bool bad(vector<int> a) {
	return a[0] + a[1] == badval;
}
bool answer(vector<int> a) {
	return a[0] + a[1] == 0;
}
// finds next bad position after pos. assumes it exists.
pair<int, vector<int>> findnext(int pos) {
	vector<int> a;
	while (!bad(a = Q(pos))) {
		if (answer(a)) return{ pos, a };
		pos++;
	}
	return{ pos, a };
}
// returns the ? in (val, val, ?, val + 1, ...). ? is the first in the sequence.
int calc(int l, int r, int val) {
	pair<int, vector<int>> b;
	int mid;
	while (l < r) {
		mid = (l + r + 1) / 2;
		b = findnext(mid);
		if (answer(b.second)) return b.first;
		if (val < b.second[0]) r = mid - 1;
		else l = mid;
	}
	return l;
}

int find_best(int n) {
	alreadyfound.clear();
	vector<int> a;
	if (n <= 5000) {
		for (int i = 0; i < n; i++) {
			a = ask(i);
			if (a[0] + a[1] == 0) return i;
		}
	}
	
	for (int i = 0; i < 500; i++) {
		auto something = Q(i);
		if (answer(something)) return i;
		badval = max(badval, something[0] + something[1]);
	}
	
	N = n;
	int l = 0, r = n - 1;
	while (!bad(a = Q(l))) {
		if (answer(a)) return l;
		l++;
	}
	while (!bad(a = Q(r))) {
		if (answer(a)) return r;
		r--;
	}
	int st = l, en, cnt;
	pair<int, vector<int>> b;
	while (st <= r) {
		en = min(r, st + 512);
		b = findnext(st);
		if (answer(b.second)) return b.first;
		st = b.first;
		b = findnext(en);
		if (answer(b.second)) return b.first;
		cnt = b.second[0] - Q(st)[0] - (b.first - en);
		for (int i = 0, tmp; i < cnt; i++) {
			tmp = calc(st, en, Q(st)[0] + i);
			if (answer(Q(tmp))) return tmp;
			if (answer(Q(tmp + 1))) return tmp + 1;
		}
		st = b.first;
	}
	return -1;
}
/*
int main() {
	int n;
	cin >> n;
	cout << find_best(n) << endl;
	cout << "^ is my answer" << endl;
}
*/

• Subtask 1: 20 / 20
• Subtask 2: 77.02 / 80