Submission #1018978

#	Time	Username	Problem	Language	Result	Execution time	Memory
1018978		j_vdd16	Counting Mushrooms (IOI20_mushrooms)	C++17	56.22 / 100	8 ms	608 KiB

mushrooms

#include "mushrooms.h"

#include <algorithm>
#include <bitset>
#include <cstdint>
#include <cstring>
#include <iostream>
#include <limits.h>
#include <math.h>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <vector>

//#define int long long
#define loop(X, N) for(int X = 0; X < (N); X++)
#define all(V) V.begin(), V.end()
#define rall(V) V.rbegin(), V.rend()

using namespace std;

typedef vector<int> vi;
typedef vector<vi> vvi;
typedef pair<int, int> ii;
typedef vector<ii> vii;
typedef vector<vector<ii>> vvii;
typedef vector<bool> vb;
typedef vector<vector<bool>> vvb;

//int use_machine(vi x);

int count_mushrooms(int n)
{
	vi a = { 0 };
	vi b;

	int i = 1;
	for (; i < n; i++)
	{
		int res = use_machine({ 0, i });
		if (res == 0)
			a.push_back(i);
		else
			b.push_back(i);

		if (a.size() >= 2 && 2 * a.size() * a.size() >= n)
			break;

		if (b.size() >= 2 && 2 * b.size() * b.size() >= n)
			break;
	}
	i++;

	int result = a.size();
	if (a.size() > b.size())
	{
		int sq = a.size();
		while (i < n)
		{
			vi ask;
			int asked = min(sq, n - i);
			loop(j, asked)
			{
				ask.push_back(a[j]);
				ask.push_back(i++);
			}

			int res = use_machine(ask);
			result += asked - res / 2 - res % 2;
		}
	}
	else
	{
		int sq = b.size();
		while (i < n)
		{
			vi ask;
			loop(j, min(sq, n - i))
			{
				ask.push_back(b[j]);
				ask.push_back(i++);
			}

			int res = use_machine(ask);
			result += res / 2 + res % 2;
		}
	}

	//226 ~ log_2(20000)^2
	//226 / Q * 100 = 52,68
	//226 * 100 / 52,68 = 429

	//S = 2 * sqrt(n);
	//S + (n - S) / sqrt(n)
	//2sqrt(n) + sqrt(n) - 2
	//3sqrt(n)

	//min: 2 * n^x + (n - 2 * n^x) / n^x
	//min: 2 * n^x + n^(1 - x) >= 2 * sqrt(2 * n)
	return result;
}

Compilation message (stderr)

mushrooms.cpp: In function 'int count_mushrooms(int)':
mushrooms.cpp:49:48: warning: comparison of integer expressions of different signedness: 'std::vector<int>::size_type' {aka 'long unsigned int'} and 'int' [-Wsign-compare]
   49 |   if (a.size() >= 2 && 2 * a.size() * a.size() >= n)
      |                        ~~~~~~~~~~~~~~~~~~~~~~~~^~~~
mushrooms.cpp:52:48: warning: comparison of integer expressions of different signedness: 'std::vector<int>::size_type' {aka 'long unsigned int'} and 'int' [-Wsign-compare]
   52 |   if (b.size() >= 2 && 2 * b.size() * b.size() >= n)
      |                        ~~~~~~~~~~~~~~~~~~~~~~~~^~~~

• Subtask 1: 56.2189 / 100