Submission #640850

#	Time	Username	Problem	Language	Result	Execution time	Memory
640850		blue	Rarest Insects (IOI22_insects)	C++17	100 / 100	56 ms	460 KiB

insects

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

using vi = vector<int>;
using vvi = vector<vi>;
#define sz(x) int(x.size())

const int mx = 2'000;

vi ins(mx, 0);
int ct = 0;

vi dp(mx + 5, 0);
vi opt(mx + 5, 0);

int getRandom(int l, int r)
{
	return rand() % (r-l+1);
}

void move_in(int i)
{
	// cerr << "insert " << i << '\n';
	if(ins[i]) 
		return;

	ins[i] = 1;
	move_inside(i);
	ct++;
}

void move_out(int i)
{
	// cerr << "erase " << i << '\n';
	if(!ins[i])
		return;

	ins[i] = 0;
	move_outside(i);
	ct--;
}

int Z = 0; //number of species

int ans = -1;

void solve(vi lst, int b) //b = basic value
{
	if(sz(lst) < Z)
		return;

	// cerr << "solve : ";
	// for(int u : lst)
	// 	cerr << u << ' ';
	// cerr << '\n';

	int mx = sz(lst)/Z;

	// int I = sz(lst);

	// int med = opt[sz(lst)];
	int med = (sz(lst)/Z)/2;
	if(med == 0)
		med++;

	// cerr << "med = " << med << '\n';

	vi ins, notins;

	int to_exc = -1;

	bool flag = 0;

	for(int t = 0; t < 10*sz(lst); t++)
	{
		int u = getRandom(0, sz(lst)-1);
		int v = getRandom(0, sz(lst)-1);
		swap(lst[u], lst[v]);
	}

	for(int i : lst)
	{
		if(ct == (med + b) * Z)
		{
			notins.push_back(i);
			continue;
		}

		move_in(i);

		int pb = press_button();

		if(pb - b > med)
		{
			move_out(i);
			notins.push_back(i);
		}
		else
		{
			if(pb - b == med && flag == 0)
			{
				to_exc = i;
				flag = 1;
			}
			ins.push_back(i);
		}
	}

	if(ct == (med + b) * Z)
	{
		solve(notins, b + med);
	}
	else
	{
		if(sz(lst) >= 2*Z)
		{
			for(int i : ins)
				move_out(i);

			vi new_ins;
			for(int i : ins)
				if(i != to_exc)
					new_ins.push_back(i);
			solve(new_ins, b);
		}
		else
			ans = (ct - sz(ins))/Z;
	}
}

int min_cardinality(int N)
{
	vi lst;
	for(int i = 0; i < N; i++)
	{
		move_in(i);
		if(press_button() >= 2)
		{
			move_out(i);
			lst.push_back(i);
		}
		else
			Z++;
	}


	// cerr << "Z = " << Z << '\n';
	for(int i = 0; i <= N; i++)
	{
		dp[i] = 5'000'000;
		opt[i] = -1;
		if(i < Z)
		{
			dp[i] = 0;
			opt[i] = 0;
		}
		else if(i < 2*Z)
		{
			dp[i] = i;
			opt[i] = 1;
		}
		else
		{
			for(int j = 1; j <= i/Z; j++)
			{
				int cand = i + max(dp[i - j*Z], dp[j*Z]);
				if(cand < dp[i])
				{
					dp[i] = cand;
					opt[i] = j;
				}
				dp[i] = min(dp[i], i + max(dp[i - j*Z], dp[j*Z]));
			}
		}

		// cerr << i << " : " << dp[i] << ' ' << opt[i] << "->" << opt[i]*Z << '\n';
	}

	solve(lst, 1);
	if(ans != -1)
		return ans;
	return ct / Z;
}

Compilation message (stderr)

insects.cpp: In function 'void solve(vi, int)':
insects.cpp:58:6: warning: unused variable 'mx' [-Wunused-variable]
   58 |  int mx = sz(lst)/Z;
      |      ^~

• Subtask 1: 10 / 10
• Subtask 2: 15 / 15
• Subtask 3: 75 / 75