Submission #1052610

#	Time	Username	Problem	Language	Result	Execution time	Memory
1052610		aykhn	Counting Mushrooms (IOI20_mushrooms)	C++17	92.24 / 100	6 ms	800 KiB

mushrooms

#include "mushrooms.h"
#include <bits/stdc++.h>
 
using namespace std;
 
int B = 70;
 
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
 
int count_mushrooms(int n) 
{
	vector<int> v[2];
	vector<int> o(n);
	iota(o.begin(), o.end(), 0);
	shuffle(o.begin() + 1, o.end(), rng);
	v[0] = {0};
	int i = 1;
	while (i < n && max(v[0].size(), v[1].size()) < 2) v[use_machine({0, o[i]})].push_back(o[i]), i++;
	for (; i < n && max(v[0].size(), v[1].size()) < B; i += 2) 
	{
		if (i + 1 < n)
		{
			if (v[0].size() >= 2)
			{
				int x = use_machine({v[0][0], o[i], v[0][1], o[i + 1]});
				v[x >> 1 & 1].push_back(o[i]);
				v[x & 1].push_back(o[i + 1]);
			}
			else
			{
				int x = use_machine({v[1][0], o[i], v[1][1], o[i + 1]});
				v[1 ^ (x >> 1 & 1)].push_back(o[i]);
				v[1 ^ (x & 1)].push_back(o[i + 1]);
			}
		}
		else v[use_machine({0, o[i]})].push_back(o[i]);
	}
	int res = 0;
	for (int j = i; j < n;)
	{
		vector<int> q;
		int l = j, r = min(n, j + (int)max(v[0].size(), v[1].size()));
		int sz = r - l;
		for (int k = l; k < r; k++)
		{
			if (v[0].size() > v[1].size())
			{
				q.push_back(v[0][k - l]);
				q.push_back(o[k]);
			}
			else
			{
				q.push_back(v[1][k - l]);
				q.push_back(o[k]);
			}
		}
		if (v[0].size() > v[1].size())
		{
			int x = use_machine(q);
			res += sz - ((x + 1) / 2);
			if (x & 1) v[1].push_back(o[r - 1]);
			else v[0].push_back(o[r - 1]), res--;
		}
		else
		{
			int x = use_machine(q);
			res += (x + 1) / 2;
			if (x & 1) v[0].push_back(o[r - 1]), res--;
			else v[1].push_back(o[r - 1]);
		}
		j = r;
	}
	return res + v[0].size();
}

Compilation message (stderr)

mushrooms.cpp: In function 'int count_mushrooms(int)':
mushrooms.cpp:19:48: warning: comparison of integer expressions of different signedness: 'const long unsigned int' and 'int' [-Wsign-compare]
   19 |  for (; i < n && max(v[0].size(), v[1].size()) < B; i += 2)
      |                  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~

• Subtask 1: 92.2449 / 100