Submission #574548

#	Time	Username	Problem	Language	Result	Execution time	Memory
574548		valerikk	The Big Prize (IOI17_prize)	C++17	90 / 100	122 ms	11276 KiB

prize

#include "prize.h"
#include <bits/stdc++.h>

using namespace std;

mt19937 rnd(239);

namespace {

int mx_cnt;

}

vector<vector<int>> mem;

vector<int> mask(int i) {
	return mem[i] == vector<int>{-1, -1} ? mem[i] = ask(i) : mem[i];
}

int solve(int l, int r) {
	if (l > r) 
		return -1;

	if (l == r) {
		auto a = mask(l);
		if (a[0] + a[1] == 0)
			return l;
		return -1;
	}

	auto al = mask(l);
	auto ar = mask(r);

	if (al[0] + al[1] == 0)
		return l;
	if (ar[0] + ar[1] == 0)
		return r;

	if (al[0] + al[1] == mx_cnt && ar[0] + ar[1] == mx_cnt && al[0] == ar[0]) 
		return -1;

	int m = (l + r) / 2;

	int res;
	if (rnd() & 1) {
		res = solve(l, m);
		if (res == -1)
			res = solve(m + 1, r);
	} else {
		res = solve(m + 1, r);
		if (res == -1)
			res = solve(l, m);
	}
	return res;
}	

int find_best(int n) {
	mem = vector<vector<int>>(n, vector<int>{-1, -1});	

	mx_cnt = 0;

	for (int i = 0; i < min(n, 500); ++i) {
		auto a = mask(i);

		if (a[0] + a[1] == 0)
			return i;

		mx_cnt = max(mx_cnt, a[0] + a[1]);
	}

	return solve(0, n - 1);
}

• Subtask 1: 20 / 20
• Subtask 2: 70 / 80