Submission #1015825

#	Time	Username	Problem	Language	Result	Execution time	Memory
1015825		Unforgettablepl	Counting Mushrooms (IOI20_mushrooms)	C++17	91.87 / 100	6 ms	700 KiB

mushrooms

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

int use_machine(vector<int> x);

const int SQRT = 100;

int strat1(int n){
	vector<bool> type(n);
	{
		int t = use_machine({0,1});
		if(t==0)type[1]=false;
		else type[1]=true;
	}
	if(n>2){
		int t = use_machine({0,2});
		if(t==0)type[2]=false;
		else type[2]=true;
	} else {
		return 1 + (int)(type[1]==false);
	}
	int a,b;bool ty;
	if(type[0]==type[1]){
		a = 0;
		b = 1;
		ty = false;
	} else if(type[0]==type[2]){
		a = 0;
		b = 2;
		ty = false;
	} else {
		a = 1;
		b = 2;
		ty = true;
	}
	type.emplace_back(false);
	for(int i=3;i<n;i+=2){
		int curr;
		if(i==n-1){
			curr = use_machine({a,i,b});
		} else {
			curr = use_machine({a,i,b,i+1});
		}
		if(curr&1){
			type[i+1] = !ty;
		} else type[i+1] = ty;
		if(curr&2){
			type[i] = !ty;
		} else type[i] = ty;
	}
	int ans = 0;
	for(int i=0;i<n;i++)if(type[i]==false)ans++;
	return ans;
}

pair<vector<int>,vector<int>> ask(){
	vector<bool> type(3*SQRT);
	int cnt_false = 1,cnt_true = 0;
	{
		int t = use_machine({0,1});
		if(t==0){type[1]=false;cnt_false++;}
		else {type[1]=true;cnt_true++;}
	}
	{
		int t = use_machine({0,2});
		if(t==0){type[2]=false;cnt_false++;}
		else {type[2]=true;cnt_true++;}
	}
	int a,b;bool ty;
	if(type[0]==type[1]){
		a = 0;
		b = 1;
		ty = false;
	} else if(type[0]==type[2]){
		a = 0;
		b = 2;
		ty = false;
	} else {
		a = 1;
		b = 2;
		ty = true;
	}
	type.emplace_back(false);
	vector<int> falses;
	vector<int> trues;
	for(int i=3;i<2*SQRT-1;i+=2){
		int curr = use_machine({a,i,b,i+1});
		if(curr&2){
			type[i] = !ty;
		} else type[i] = ty;
		if(curr&1){
			type[i+1] = !ty;
		} else type[i+1] = ty;
	}
	for(int i=0;i<2*SQRT-1;i++)if(type[i])trues.emplace_back(i);
	for(int i=0;i<2*SQRT-1;i++)if(!type[i])falses.emplace_back(i);
	return {falses,trues};
}

int count_mushrooms(int n) {
	if(n<=450)return strat1(n);
	auto [falses,trues] = ask();
	int ans = falses.size();
	for(int i=2*SQRT-1;i<n;){
		vector<int> buffer;
		int siz = max(falses.size(),trues.size());
		for(int j=0;j<siz;j++)if(i+j<n)buffer.emplace_back(i+j);
		i+=siz;
		vector<int> query;
		query.emplace_back(buffer.front());
		auto iter = buffer.begin()+1;
		bool type;
		if(falses.size()<trues.size())type = true;
		else type = false;
		auto iterb = trues.begin();
		if(type)iterb = trues.begin();
		else iterb = falses.begin();
		while(iter!=buffer.end()){
			query.emplace_back(*iterb++);
			query.emplace_back(*iter++);
		}
		query.emplace_back(*iterb++);
		if(type){
			int t = use_machine(query);
			if(t&1)falses.emplace_back(query.front());
			else trues.emplace_back(query.front());
			t++;t/=2;
			ans+=t;
		} else {
			int t = use_machine(query);
			if(t&1)trues.emplace_back(query.front());
			else falses.emplace_back(query.front());
			t++;t/=2;
			ans+=buffer.size()-t;
		}
	}
	return ans;
}

• Subtask 1: 91.8699 / 100