Submission #1014881

#	Time	Username	Problem	Language	Result	Execution time	Memory
1014881		Unforgettablepl	Counting Mushrooms (IOI20_mushrooms)	C++17	80.14 / 100	8 ms	600 KiB

mushrooms

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

int use_machine(vector<int> x);

const int SQRT = 147;

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;
}

int checked_until = -1;

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<3*SQRT;i+=2){
		int curr = use_machine({a,i,b,i+1});
		if(curr&2){
			type[i] = !ty;
		} else type[i] = ty;
		checked_until = i+1;
		if(type[i]==false){
			if(++cnt_false==SQRT)break;
		} else {
			if(++cnt_true==SQRT)break;
		}
		if(curr&1){
			type[i+1] = !ty;
		} else type[i+1] = ty;
		checked_until = i+2;
		if(type[i+1]==false){
			if(++cnt_false==SQRT)break;
		} else {
			if(++cnt_true==SQRT)break;
		}
	}
	vector<int> ans;
	bool tar;
	if(cnt_false==SQRT)tar = false;
	else tar = true;
	for(int i=0;i<checked_until;i++)if(type[i]==tar)ans.emplace_back(i);
	assert(ans.size()==SQRT);
	return ans;
}

int count_mushrooms(int n) {
	if(n<=450)return strat1(n);
	auto idx = ask();
	bool ty = idx.front()!=0;
	int ans = 0;
	if(ty){
		ans = checked_until-SQRT;
		for(int i=checked_until;i<n;i+=SQRT){
			vector<int> buffer;
			for(int j=0;j<SQRT;j++)if(i+j<n)buffer.emplace_back(i+j);
			vector<int> query;
			query.emplace_back(buffer.front());
			auto iter = buffer.begin()+1;
			auto iterb = idx.begin();
			while(iter!=buffer.end()){
				query.emplace_back(*iterb++);
				query.emplace_back(*iter++);
			}
			query.emplace_back(idx.back());
			int t = use_machine(query);t++;t/=2;
			ans+=t;
		}
	} else {
		ans = SQRT;
		for(int i=checked_until;i<n;i+=SQRT){
			vector<int> buffer;
			for(int j=0;j<SQRT;j++)if(i+j<n)buffer.emplace_back(i+j);
			vector<int> query;
			query.emplace_back(buffer.front());
			auto iter = buffer.begin()+1;
			auto iterb = idx.begin();
			while(iter!=buffer.end()){
				query.emplace_back(*iterb++);
				query.emplace_back(*iter++);
			}
			query.emplace_back(idx.back());
			int t = use_machine(query);t++;t/=2;
			ans+=buffer.size()-t;
		}
	}
	return ans;
}

• Subtask 1: 80.1418 / 100