Submission #781050

#	Time	Username	Problem	Language	Result	Execution time	Memory
781050		Elias	Counting Mushrooms (IOI20_mushrooms)	C++17	87.94 / 100	9 ms	384 KiB

mushrooms

#ifndef _DEBUG
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#endif

#include <bits/stdc++.h>

using namespace std;

#ifdef _DEBUG

int count_mushrooms(int n);

int use_machine(std::vector<int> x);
#endif

#ifndef _DEBUG
#include "mushrooms.h"
#endif

int count_mushrooms(int n)
{
	int countA = 1;
	int countB = 0;
	set<int> a = {0};
	set<int> b;

	int queries = 0;

	int i = 1;

	while (a.size() < 2 && b.size() < 2 && i != n)
	{
		if (use_machine({0, i}))
		{
			b.insert(i++);
			countB++;
		}
		else
		{
			a.insert(i++);
			countA++;
		}
		queries++;
	}

	bool swapped = false;

	if (b.size() > a.size())
	{
		swap(a, b);
		swap(countA, countB);
		swapped ^= true;
	}

	while ((n - i) > queries * a.size() && (n - i) > queries * b.size() && i != n)
	{
		int output = use_machine({*a.begin(), i, *next(a.begin()), i + 1});
		queries++;
		if (output & 2)
			b.insert(i), countB++;
		else
			a.insert(i), countA++;

		if (output & 1)
			b.insert(i + 1), countB++;
		else
			a.insert(i + 1), countA++;

		i += 2;
	}

	while (i != n)
	{
		if (b.size() > a.size())
		{
			swap(a, b);
			swap(countA, countB);
			swapped ^= true;
		}

		vector<int> query;

		vector<int> copyA(a.begin(), a.end());
		reverse(copyA.begin(), copyA.end());

		while (i != n && copyA.size())
		{
			query.push_back(copyA.back());
			query.push_back(i++);
			copyA.pop_back();
		}

		int output = use_machine(query);

		int newB = (output + 1) / 2;
		int newA = query.size() / 2 - newB;

		countA += newA;
		countB += newB;

		if (output & 1)
		{
			b.insert(query.back());
		}
		else
		{
			a.insert(query.back());
		}
	}

	if (swapped)
	{
		swap(a, b);
		swap(countA, countB);
	}
	return countA;
}

#ifdef _DEBUG

static char fmt_buffer[100000];
#define FMT_TO_STR(fmt, result)                            \
	va_list vargs;                                         \
	va_start(vargs, fmt);                                  \
	vsnprintf(fmt_buffer, sizeof(fmt_buffer), fmt, vargs); \
	va_end(vargs);                                         \
	fmt_buffer[sizeof(fmt_buffer) - 1] = 0;                \
	std::string result(fmt_buffer);

static const int min_n = 2;
static const int max_n = 20000;
static const int max_qc = 20000;
static const int max_qs = 100000;
static const int species_A = 0;
static const int species_B = 1;

static int n;
static std::vector<int> species;
static int qc, qs;

static inline void error_if(bool cond, std::string message)
{
	if (cond)
	{
		printf("%s\n", message.c_str());
		exit(0);
	}
}

static inline void wrong_if(bool cond, std::string message)
{
	error_if(cond, "Wrong Answer: " + message);
}

int use_machine(std::vector<int> x)
{
	const int xs = x.size();
	wrong_if(xs < 2, "Too small array for query.");
	wrong_if(xs > n, "Too large array for query.");
	qc++;
	wrong_if(qc > max_qc, "Too many queries.");
	qs += xs;
	wrong_if(qs > max_qs, "Too many total array sizes as queries.");
	for (int i = 0; i < xs; i++)
		wrong_if(x[i] < 0 || n - 1 < x[i], "Invalid value in the query array.");
	std::vector<bool> used(n, false);
	for (int i = 0; i < xs; i++)
	{
		wrong_if(used[x[i]], "Duplicate value in the query array.");
		used[x[i]] = true;
	}
	int diffs = 0;
	for (int i = 1; i < xs; i++)
		diffs += int(species[x[i]] != species[x[i - 1]]);
	return diffs;
}

#ifdef __GNUC__
__attribute__((format(printf, 2, 3)))
#endif
static inline void
check_input(bool cond, const char *message_fmt, ...)
{
	FMT_TO_STR(message_fmt, message);
	error_if(!cond, "Invalid input: " + message);
}

int main()
{
	check_input(1 == scanf("%d", &n), "Could not read n.");
	check_input(min_n <= n, "n must not be less than %d, but it is %d.", min_n, n);
	check_input(n <= max_n, "n must not be greater than %d, but it is %d.", max_n, n);
	species.resize(n);
	for (int i = 0; i < n; i++)
	{
		check_input(1 == scanf("%d", &species[i]), "Could not read species element [%d].", i);
		check_input(species[i] == species_A || species[i] == species_B,
					"Species elements must be %d or %d, but species element [%d] is %d.", species_A, species_B, i, species[i]);
	}
	check_input(species[0] == species_A, "Species element [%d] must be %d.", 0, species_A);
	// Postponed closing standard input in order to allow interactive usage of the grader.

	qc = 0;
	qs = 0;
	int answer = count_mushrooms(n);
	printf("%d\n%d\n", answer, qc);
	fclose(stdout);
	fclose(stdin);
	return 0;
}

#endif

Compilation message (stderr)

mushrooms.cpp: In function 'int count_mushrooms(int)':
mushrooms.cpp:56:17: warning: comparison of integer expressions of different signedness: 'int' and 'std::set<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   56 |  while ((n - i) > queries * a.size() && (n - i) > queries * b.size() && i != n)
      |         ~~~~~~~~^~~~~~~~~~~~~~~~~~~~
mushrooms.cpp:56:49: warning: comparison of integer expressions of different signedness: 'int' and 'std::set<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   56 |  while ((n - i) > queries * a.size() && (n - i) > queries * b.size() && i != n)
      |                                         ~~~~~~~~^~~~~~~~~~~~~~~~~~~~

• Subtask 1: 87.9377 / 100