Submission #303752

#	Time	Username	Problem	Language	Result	Execution time	Memory
303752		aljasdlas	Counting Mushrooms (IOI20_mushrooms)	C++14	80.43 / 100	14 ms	584 KiB

mushrooms

#include "mushrooms.h"
#include <bits/stdc++.h>
using namespace std;

int count_mushrooms(int n) {
	if(n < 220) {
		int B = 0;
		for(int i = 1; i < n; i++) {
			B += use_machine({0, i});
		}
		return n-B;
	}

	vector<int> perm;
	for(int i = 1; i < n; i++)
		perm.push_back(i);
	
	srand(time(0));
	random_shuffle(perm.begin(), perm.end());
	reverse(perm.begin(), perm.end());
	perm.push_back(0);
	reverse(perm.begin(), perm.end());

	vector<int> A, B;
	A = {0};
	if(use_machine({0,perm[1]})) B.push_back(perm[1]);
	else A.push_back(perm[1]);
	if(use_machine({0,perm[2]})) B.push_back(perm[2]);
	else A.push_back(perm[2]);

	if(B.size() > A.size()) swap(A,B);

	for(int i = 3; i < n && A.size()*A.size() < (n-A.size()-B.size()) && B.size()*B.size() < (n-A.size()-B.size()); i+=2) {
		vector<int> cur;
		cur.push_back(A[0]);
		cur.push_back(perm[i]);
		cur.push_back(A[1]);
		if(i+1 < n) cur.push_back(perm[i+1]);

		// for(auto x: cur) cerr << x << " ";
		// cerr << endl;
		int res = use_machine(cur);

		if(res & 2) B.push_back(perm[i]);
		else A.push_back(perm[i]);

		if(i+1 < n) {
			if(res & 1) B.push_back(perm[i+1]);
			else A.push_back(perm[i+1]);
		}
	}

	if(B.size() > A.size()) swap(A,B);

	int countA = 0;
	int countB = 0;
	for(int i = A.size()+B.size(); i < n; i+=A.size()) {
		vector<int> cur;
		int j = 0;
		for(j = 0; i+j < n && j < A.size(); j++) {
			cur.push_back(A[j]);
			cur.push_back(perm[i+j]);
		}

		// for(auto x: cur) cerr << x << " ";
		// cerr << ": ";
		int res = use_machine(cur);
		countB += (res+1)/2;
		countA += j - ((res+1)/2);
		// cerr << res << " -> " << countA << " " << countA << endl;;
	}

	if(A[0] == 0) return A.size()+countA;
	else return B.size()+countB;
}

Compilation message (stderr)

mushrooms.cpp: In function 'int count_mushrooms(int)':
mushrooms.cpp:60:27: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   60 |   for(j = 0; i+j < n && j < A.size(); j++) {
      |                         ~~^~~~~~~~~~

• Subtask 1: 80.427 / 100